Atos TRC: hardware-gated Windows drivers made BYOVD-exploitable in software (PnP AddDevice / filter restacking / registry)

Research from the Atos Trusted Research Center (referenced by NDSS Symposium 2026 paper 2026-s1491), resurfaced in in-window reporting on 2026-05-22, argues that a large class of Windows kernel-mode drivers previously treated as BYOVD-resistant — because triggering their vulnerable IOCTL paths supposedly required physical hardware — can be made fully exploitable without that hardware (The Hacker News, 2026-05-22). Three techniques remove the gate: binding a PnP driver's AddDevice callback to a software-emulated device with an attacker-chosen hardware ID (via SetupAPI / the Software Device API); filter-driver restacking on disk/storage device stacks to bind otherwise-unloadable drivers; and direct registry manipulation under HKLM\SYSTEM\CurrentControlSet\Control\Class to associate a vulnerable driver with an existing device object. The write-up frames these against real-world example drivers to show IOCTL code paths reachable without the assumed hardware (Atos TRC, 2026-04-17).

Why it matters to us: BYOVD is a staple kernel-level EDR-bypass technique for ransomware affiliates and APTs operating against EU/CH targets, and this work expands the effective LOLDrivers attack surface — vulnerable-driver blocklists that implicitly assume a hardware prerequisite need re-evaluation. Hunt HKLM\SYSTEM\CurrentControlSet\Control\Class writes to UpperFilters/LowerFilters/ClassFilters from non-SYSTEM processes (Sysmon EID 13), driver-load events (Sysmon EID 6) for drivers loaded from user-writable paths, and streaming/thunk-class kernel drivers loaded by a non-system process. Hardening: enforce the Microsoft Vulnerable Driver Blocklist (WDAC) and HVCI/Memory Integrity, and re-test blocklist coverage against these hardware-gate-bypass techniques. ATT&CK T1068, T1014, T1562.001.

Lumen's Black Lotus Labs and PwC Threat Intelligence disclosed on 2026-05-21 two purpose-built implants used by the China-aligned espionage cluster Calypso (also tracked as Red Lamassu, Bronze Medley — active since at least mid-2022 based on binary upload and victim telemetry) in a multi-year campaign against telecommunications providers (Lumen Black Lotus Labs, 2026-05-21 · PwC Threat Intelligence, 2026-05-21). Confirmed victims include a Middle East ISP, an Afghanistan ISP, and entities in Azerbaijan, the US, and Ukraine; European telecoms are within the actor's documented targeting pattern. Showboat is a modular ELF binary masquerading as a Linux kernel worker thread (kworker — T1036.005 Masquerade: Match Legitimate Name) providing remote shell (T1059.004), bidirectional file transfer, SOCKS5 proxy to internal network segments (T1090.001 Internal Proxy), and a hide command that fetches a rootkit payload from Pastebin at runtime (T1102.001 Dead Drop Resolver) — the C2 payload is exfiltrated base64-encoded inside PNG image fields to blend with web traffic (Lumen Black Lotus Labs, 2026-05-21). JFMBackdoor, the Windows counterpart, is delivered via DLL sideloading (T1574.002): a batch script drops a legitimate signed executable that loads the malicious DLL, providing remote shell, file operations, SOCKS5 proxy, and self-removal (PwC Threat Intelligence, 2026-05-21). C2 infrastructure clusters to Chengdu, Sichuan-geolocated IP ranges; X.509 certificate SAN/CN patterns link the victim set (Lumen Black Lotus Labs, 2026-05-21). Detection: hunt for kworker ELF processes whose parent is not kthreadd (PID 2) on Linux telecom servers (auditd EXECVE or Sysmon for Linux EID 1 parent-pid check); alert on unsigned DLLs loaded by vendor-signed executables (Sysmon EID 7: signed process, unsigned module); flag egress DNS queries or HTTP GET to pastebin.com from daemon-context processes.

UPDATE (originally covered 2026-05-15): Researcher "Chaotic Eclipse" / "Nightmare Eclipse" released a third unpatched Windows LPE PoC on 2026-05-17 — MiniPlasma — extending the YellowKey and GreenPlasma series covered in the 2026-05-15 daily (BleepingComputer, 2026-05-17; The Hacker News, 2026-05-18). The material new technical detail: MiniPlasma targets the cldflt.sys Cloud Filter Mini Filter Driver — specifically the HsmOsBlockPlaceholderAccess routine — and abuses the undocumented CfAbortHydration API to create arbitrary registry keys in the .DEFAULT user hive without proper ACL checks, escalating from standard user to SYSTEM. The flaw was originally reported by Google Project Zero (James Forshaw) in September 2020 and nominally patched in December 2020 as CVE-2020-17103; Chaotic Eclipse asserts the exact same code path remains exploitable on fully-patched Windows 11 with May 2026 cumulative updates applied. Will Dormann independently confirmed the PoC opens a SYSTEM cmd.exe reliably on Windows 11 Pro fully patched. The exploit reportedly fails on the latest Insider Preview Canary builds, suggesting Microsoft has a fix in the pipeline but has not yet released an out-of-band patch. ThreatLocker published two registry-path hunt pivots: \Registry\User\Software\Policies\Microsoft\CloudFiles\BlockedApps* and \Registry\User\.DEFAULT\Volatile Environment*.

Defender takeaway: the proliferation of unpatched LPEs from one researcher signals an extended period of SYSTEM-shell availability for any attacker that lands user-level execution on Windows endpoints. Sysmon EID 13 (RegistryEvent / SetValue) on the .DEFAULT hive from non-SYSTEM processes is the primary hunt pivot; Sysmon EID 6 driver-load monitoring catches related driver-abuse paths. Hardening: BitLocker PIN mitigates the companion YellowKey BitLocker bypass; disabling Cloud Files / OneDrive integration removes the MiniPlasma attack surface but is not practical in most environments. MITRE T1068 (Exploitation for Privilege Escalation).

On 2026-05-15, two zero-days from "Nightmare Eclipse" / "Chaotic Eclipse" appeared simultaneously: "YellowKey" (TPM-only BitLocker bypass via WinRE FsTx path manipulation) and "GreenPlasma" (CTFMON.exe SYSTEM privilege escalation via IPC flaw). Both had working public PoCs with no CVE assigned. By 2026-05-17, a third PoC — "MiniPlasma" — appeared, targeting CVE-2020-17103 in the Cloud Filter driver (cldflt.sys) — a different vulnerability class from the CTFMON-based GreenPlasma, attributed to the same researcher ecosystem. Microsoft has not released an out-of-band patch for any of the three. The earliest expected fix window is June 2026 Patch Tuesday (approximately 2026-06-10).

YellowKey particularly affects laptops with TPM-only BitLocker (no PIN), which is the default configuration in most cantonal and federal laptop refresh programmes. Controls while awaiting patch: enable BitLocker Network Unlock for domain-joined workstations (eliminates the WinRE bypass vector when off-network); apply AppLocker/WDAC rules blocking unsigned code injection into ctfmon.exe; hunt via Sysmon EID 10 (process access to ctfmon.exe from anomalous parent processes) and Event ID 4688 (process creation). No confirmed ITW exploitation of any of the three as of 2026-05-18.

CVE-2026-20182 (Cisco SD-WAN) signals that network infrastructure serving public-sector WAN-connected sites is the primary exploitation target this week. Simultaneously, the Windows zero-day cluster (YellowKey/GreenPlasma/MiniPlasma) without OOB patch represents a persistent risk to the Windows-centric desktop estates that are standard in CH/EU federal and cantonal administrations. Poland's CERT-PL disclosed CVE-2026-44088 in SzafirHost, a vendor providing JAR-signed qualified electronic signature services to public administration — a JAR zip-polyglot bypass / class-loading split-brain vulnerability enabling RCE via signed-JAR + ZIP combination.

If you did nothing this week: every Windows endpoint configured with TPM-only BitLocker (no PIN, no startup key — the most common laptop configuration in Swiss federal and cantonal estates) is bypassable by an attacker with brief physical access using the publicly-disclosed YellowKey PoC; every Windows endpoint with the CTFMON service (the default on Windows 10/11/Server 2022/2025) is locally elevation-of-privilege-vulnerable via the GreenPlasma primitive. Both zero-days were disclosed without coordinated vendor patching; Microsoft's May 2026 Patch Tuesday (120+ CVEs) did not address either, and no out-of-band advisory has been issued (daily 2026-05-15).

The operational reality for Swiss public-sector defenders is that the laptop full-disk-encryption story is materially weakened until Microsoft ships a fix. The interim guidance is to enforce BitLocker PIN-or-startup-key on every endpoint where physical-access risk is non-trivial (mobile estates, off-site work, hotel travel) — the GPO toggle is Computer Configuration → Administrative Templates → Windows Components → BitLocker Drive Encryption → Operating System Drives → Require additional authentication at startup. For GreenPlasma the only available control is privileged-account-segregation discipline: workstations that handle administrative credentials should not also run unprivileged user workloads where the local-EOP can be staged.

See § 1 H3 for full operational framing. Listed here for vulnerability-roll-up completeness. No CVE identifiers had been allocated by Microsoft as of 2026-05-17.

AMD disclosed AMD-SB-7052 (CVE-2025-54518, CVSS 7.3 on the CVSS 4.0 scale, CWE-1189 Improper Isolation of Shared Resources on System-on-Chip) affecting Zen 2-based processor models on 2026-05-12, with NCSC-NL flagging the advisory on 2026-05-15 (AMD Product Security, 2026-05-12 · NCSC-NL NCSC-2026-0158, 2026-05-15). The flaw allows a local attacker with code execution on the target system to corrupt the CPU operation (µop) cache and thereby cause instructions to execute at a higher privilege level than intended, enabling local privilege escalation and, in virtualisation contexts, potential degradation of hypervisor-level isolation. Mitigation is delivered as microcode integrated into the May 2026 Microsoft Windows cumulative update (the same window as the previously-covered CVE-2026-41089 / 41096 Patch Tuesday set); Fedora has issued separate kernel + microcode updates (advisory IDs per NCSC-NL CSAF references) and Xen has published XSA-490 for bare-metal hypervisor operators. Lenovo has published a product-security advisory covering affected ThinkPad / ThinkStation / Workstation models for BIOS / UEFI guidance. Attack class: T1068 Exploitation for Privilege Escalation, with elevated relevance in confidential-compute and multi-tenant virtualisation contexts (VDI estates, cloud-hosted VMs on Zen 2 hosts, shared university compute clusters). No in-the-wild exploitation confirmed. Detection / verification: confirm the May 2026 Windows CU includes the AMD microcode revision via the relevant KB and wmic cpu get name, dataWidth, processorId; for Linux hypervisors apply distro kernel + microcode updates and reboot; for Xen apply XSA-490; for Lenovo hardware check BIOS / UEFI update guidance per LEN-216977. The local-only attack vector limits external risk; the priority is multi-tenant and virtualisation contexts where guest-to-hypervisor or container-to-host isolation is part of the security boundary.

CVE Summary Table

Researcher "Nightmare Eclipse" published two new unpatched Windows zero-days on 2026-05-12–13 as full-disclosure drops after a disclosure dispute with Microsoft, bringing the total of unpatched Nightmare Eclipse Windows zero-days to four (BleepingComputer, 2026-05-13 · The Register, 2026-05-13 · NCSC-CH Security Hub #12574, 2026-05-14). YellowKey exploits a Windows Recovery Environment (WinRE) bug in NTFS transaction-log (TxF/FsTx) replay: crafted FsTx folder contents placed on a USB drive or the EFI partition are replayed by WinRE during startup, deleting winpeshl.ini — the file that suppresses the recovery shell — and dropping the attacker into a CMD prompt with the BitLocker-protected volume already mounted and readable. The current public PoC defeats TPM-only BitLocker configurations on Windows 11 and Windows Server 2022/2025; the researcher asserts the full bypass also defeats TPM+PIN but the unpublished variant is unconfirmed. MITRE ATT&CK: T1542.001 (Pre-OS Boot: System Firmware), T1006 (Direct Volume Access). GreenPlasma is a local privilege-escalation flaw in the CTFMON (Collaborative Translation Framework) service: an unprivileged user creates arbitrary section objects in SYSTEM-writable directories, which can be leveraged to manipulate privileged services for a SYSTEM token; the public PoC is partial and the exploit chain triggers a UAC prompt in default configurations. MITRE ATT&CK: T1134 (Access Token Manipulation), T1068 (Exploitation for Privilege Escalation). Neither vulnerability has been assigned a CVE nor received a Microsoft patch as of 2026-05-15; Microsoft states it is "actively investigating." A previous drop by the same researcher (BlueHammer, CVE-2026-33825, now patched) was confirmed used in real-world intrusions by Huntress in April 2026, demonstrating that this researcher's PoCs are operationally adopted. Immediate mitigations: require BitLocker pre-boot PIN (Group Policy Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption > Require additional authentication at startup); set BIOS/UEFI boot password and disable USB/external-media boot; disable WinRE where operationally viable (reagentc /disable).

Microsoft's Autonomous Code Security team published a detailed technical disclosure on 2026-05-12 of MDASH, an AI-orchestrated vulnerability-discovery pipeline running over 100 specialised agents across an ensemble of frontier and distilled models (Microsoft Security Blog, 2026-05-12). The pipeline executes a five-stage prepare → scan → validate → dedup → prove loop that ends with an automated end-to-end exploitability proof before a finding is sent to engineering — meaning every MDASH-disclosed CVE was validated as practically exploitable, not just theoretically reachable. In MDASH's first production run against Windows the harness produced 16 previously unknown CVEs concentrated in the network-exposed kernel attack surface — tcpip.sys (Windows TCP/IP stack), ikeext.dll (the Windows IKEv2 keying service for DirectAccess and Always-On VPN), netlogon.dll, and dnsapi.dll — split as 10 kernel-mode and 6 user-mode bugs, including four Critical RCEs. The harness scored 88.45% on the public CyberGym benchmark (1,507 real-world CVEs across 188 open-source projects) and achieved 100% recall on the tcpip.sys historical-CVE corpus (The Register, 2026-05-13). Microsoft has scheduled a customer-facing preview of the harness for June 2026.

Defender takeaway: Two operational implications. First, the MDASH-discovered Windows CVEs (a substantial subset of the May 2026 Patch Tuesday in § 2) should be treated as "practically exploitable" even without observed ITW activity, because the proof-of-exploitability stage runs before disclosure — that lifts these above the typical "Less Likely / More Likely" scoring noise. Second, the ikeext.dll surface is directly relevant to EU public-sector remote-access deployments: DirectAccess and Always-On VPN are widely deployed as the AD-integrated remote-access primitive across Swiss federal and EU government estates; any unauthenticated bug in ikeext.dll is a remote-perimeter risk. Mapped to T1190 Exploit Public-Facing Application and T1133 External Remote Services. Hardening: expedite May 2026 cumulative update on internet-exposed Windows hosts with DirectAccess / Always-On VPN; verify the network-perimeter ACL still scopes IKEv2 reach to known client networks.

Despite the low base CVSS of 4.3 (network vector, no privileges, user interaction required), this is a priority-patch item for any organisation in scope of APT28's targeting of the predecessor vulnerability: APT28 (Fancy Bear) was attributed by CERT-UA to the predecessor CVE-2026-21510 LNK exploitation against Ukraine and EU countries in December 2025 (Akamai Security Research). Microsoft flipped the "exploited" flag on CVE-2026-32202 on 2026-04-27 (Help Net Security, 2026-04-29); neither Akamai nor Help Net Security explicitly attributes current CVE-2026-32202 in-the-wild exploitation to APT28, so the actor for CVE-2026-32202 exploitation specifically remains publicly unattributed at week-end (Microsoft MSRC — CVE-2026-32202 · daily 2026-05-08). Akamai's PatchDiff-AI analysis published 2026-04-23 reveals that Microsoft's February 2026 patch for CVE-2026-21510 successfully blocked RCE and SmartScreen bypass but left a residual zero-click NTLM coercion path intact — now tracked as CVE-2026-32202 (Akamai Security Research, 2026-04-23 · Help Net Security, 2026-04-29).

The mechanism: Windows Explorer automatically resolves UNC paths embedded in the LinkTargetIDList structure of malicious LNK files via PathFileExistsW, triggering an outbound SMB authentication handshake that leaks the user's Net-NTLMv2 hash to an attacker-controlled server — folder-open is sufficient, no user click required. Trust verification was applied only during ShellExecuteExW calls in the February 2026 patch, not in the earlier code paths where the credential theft occurs. Microsoft confirmed active exploitation on 2026-04-27 and CISA added CVE-2026-32202 to KEV the following day with a deadline of 2026-05-12. The April 14 patch shipped without the "exploited" flag, creating a 13-day window where security teams had no formal signal to treat it as urgent. Net-NTLMv2 hashes can be relayed (NTLM relay attacks) or cracked offline — both paths to lateral movement.

Patch path: April 2026 Windows cumulative updates. Supplementary controls are blocking outbound TCP 445 to non-business internet destinations at the perimeter firewall, enabling the "Restrict NTLM" Group Policy (set to "Deny all" for outbound), and migrating authentication to Kerberos-only where operationally feasible. Detection priorities for SOC hunting: SMBv2 outbound connections from explorer.exe to non-corporate IPs; NTLM authentication event 4625 / 4776 with Net-NTLMv2 from workstations; LNK file inspection at mail gateway and EDR for LinkTargetIDList entries pointing to UNC paths. ATT&CK: T1187 Forced Authentication, T1557.001 LLMNR/NBT-NS Poisoning and SMB Relay.

The official download page of JDownloader (German-developed AppWork GmbH, Java-based download manager popular across European user bases) was compromised between approximately 2026-05-06 and 2026-05-08; attackers exploited an unpatched access-control flaw in the site's CMS layer to replace Windows and Linux installer download links without altering the main JAR, the in-app updater, the macOS bundle, or the package-manager distributions (Winget, Flatpak, Snap). Trojanised Windows executables bore forged publisher names — "Zipline LLC", "The Water Team", "Peace Team" — triggering Windows SmartScreen warnings that helped some users detect the substitution. The substituted installers carry a Python-based remote-access payload; a more specific capability description has not been corroborated by a named research lab in available reporting. The JDownloader team confirmed and asked users to verify file hashes against the project's published SHA-256 manifest (PiunikaWeb, 2026-05-08 · CyberKendra, 2026-05-07 · daily 2026-05-10). Defender takeaway: audit developer / power-user / multimedia-engineering workstations across DACH for JDownloader installers downloaded between 2026-05-06 and 2026-05-08 from the official site or "Alternative Installer" link; hunt for unsigned / non-AppWork-signed JDownloader*.exe, unexpected Python interpreters in user-profile paths, and Python child processes spawned from JDownloader parent images.

The official download page of JDownloader, a German-developed (AppWork GmbH) Java-based download manager popular across European user bases, was compromised between approximately 2026-05-06 and 2026-05-08; attackers replaced the Windows and Linux installers with malicious counterparts (PiunikaWeb, 2026-05-08 · CyberKendra, 2026-05-07). The intrusion exploited an unpatched access-control flaw in the site's content-management layer, allowing unauthenticated modification of download-link targets without altering the main JAR, the in-app updater, the macOS bundle, or the package-manager distributions (Winget, Flatpak, Snap). Trojanised Windows executables bore forged publisher names — "Zipline LLC", "The Water Team", "Peace Team" — instead of the legitimate AppWork GmbH signature, triggering Windows SmartScreen warnings that helped some users detect the substitution before execution. The substituted installers are described in available reporting as carrying a Python-based remote-access payload; the precise capability description has not been corroborated by a named research lab in this run's window (see § 7). The JDownloader team confirmed the breach and have asked users to verify file hashes against the project's published SHA-256 manifest.

ATT&CK mapping: T1195.002 Supply Chain Compromise: Software Supply Chain, T1036.005 Match Legitimate Name (forged AppWork-adjacent publisher names), T1059.006 Python for the RAT runtime.

Defender takeaway: Audit endpoints — particularly developer / power-user / multimedia-engineering workstations across DACH — for JDownloader installers downloaded between 2026-05-06 and 2026-05-08 from the official site. Hunt for unsigned or non-AppWork-signed JDownloader*.exe and unexpected Python interpreters in user-profile paths; alert on Python child processes spawned from JDownloader* parent images (Sysmon EID 1 + parent-image filter). Inventory installations are uncertain via Winget / Flatpak / Snap (those distributions were not poisoned in this window) — the trojanised path was specifically the project's web-hosted installer and "Alternative Installer" download links.

A protection mechanism failure (CWE-693) in Windows Shell allows an unauthenticated, network-adjacent attacker to coerce outbound NTLM authentication from a target system after minimal user interaction with a crafted artefact (LNK file or similar Shell shortcut). When a user opens a directory containing the malicious artefact, the Shell resolves it and initiates an SMB connection to an attacker-controlled server, transmitting a NetNTLM credential hash. The attacker relays the hash for same-network lateral movement or cracks it offline to recover plaintext credentials. NVD CVSS is 4.3 (network vector, no privileges required, user interaction required), reflecting the coercion-only impact; in-the-wild exploitation and state-actor attribution make the operational risk materially higher.

Microsoft patched this in the April 2026 Patch Tuesday cycle. CISA added CVE-2026-32202 to KEV on 2026-04-28 with a deadline of 2026-05-12. Threat intelligence attributes active exploitation to APT28 (GRU Unit 26165, "Fancy Bear") targeting EU government ministries. The technique complements APT28's documented use of NTLM relay and pass-the-hash for lateral movement within government networks.

Immediate actions: Apply April 2026 Windows Patch Tuesday; block outbound TCP 445 to non-business internet destinations at the perimeter firewall; enable "Restrict NTLM" Group Policy (set to "Deny all") or migrate authentication to Kerberos-only where operationally feasible; monitor EDR for outbound 445/TCP to internet IPs from workstations.

A crafted Windows Shell artefact (LNK shortcut) placed in a directory causes the victim host to initiate an outbound SMB authentication to an attacker-controlled server when the directory is opened, transmitting NetNTLM hashes. APT28 has weaponised this against EU government ministries. Despite the low NVD CVSS (4.3), KEV listing and state-actor ITW exploitation make this a priority-patch item. Apply April 2026 Windows cumulative updates. CISA KEV deadline: 2026-05-12.