2026-09-06 · view entry permalink →
Chaotic Eclipse turns its zero-day drops on third-party security products: unpatched local privilege escalation in CrowdStrike Falcon and Avast, with working proof-of-concept code public
The pseudonymous researcher tracked here as Nightmare Eclipse, and by The Hacker News under the further aliases Chaotic Eclipse, INFINITE NIGHTMARE and MSNightmare, spent 2026 publishing working proof-of-concept exploits for Windows and Microsoft Defender privilege escalations without giving the vendor advance notice. In early September the target set changed: three of the four latest drops are against third-party endpoint security products rather than Microsoft's, and two of them have no fix (The Hacker News, 2026-09-03). That shift is what makes this an operational matter for estates that never had Defender in scope.
FalconFlank abuses CrowdStrike Falcon Sensor's Office malicious-macro remediation path. The remediation routine runs at high privilege in order to clean an infected document in place, and the exploit turns that cleanup into a low-privileged account's route to SYSTEM. Truesec, reading the release independently, records the preconditions precisely: the proof-of-concept "works in a fully updated windows 11 25H2 / Windows Server 2025 with Crowdstrike Falcon – Phase 3 Optimal Protection with 'Microsoft Office file malicious macro removal' setting" (Truesec, 2026-09-04). A CrowdStrike spokesperson told The Hacker News the company is "actively investigating these claims and advise customers to disable the Microsoft Office File Suspicious Macro Removal Windows policy setting", adding that customers "remain protected through the Cloud Anti-malware for Microsoft Office Files settings" (The Hacker News, 2026-09-03). There is no patch and no CVE; the control on offer is turning a prevention feature off, which Truesec notes means malicious macros will no longer be replaced in place while cloud-side blocking continues (Truesec, 2026-09-04).
PrettyPrague is the same shape against a different vendor. The researcher describes it as dumping the SAM database "by abusing a vulnerability in Avast Sandbox" and spawning a full SYSTEM shell against fully patched Avast Antivirus on a patched Windows 11 25H2 host, and states a belief that other Gen Digital products including AVG and Norton are affected (The Hacker News, 2026-09-03). Gen Digital confirmed a vulnerability "affecting a subset of Gen products, including Avast Antivirus, that could allow an attacker to elevate their system privileges" and said it is "actively developing a patch", without naming which further products are in scope (The Hacker News, 2026-09-03). The third drop, HardBreacher against Kaspersky Endpoint Security for Windows 14.0.0.504, is the one that is resolved: Kaspersky told the same outlet the fix ships through an automatic database update or a manually triggered one (The Hacker News, 2026-09-03). A fourth release, GreenSection, is described only as an NVIDIA memory-corruption bug that crashes any application using Vulkan or OpenGL, rather than a privilege escalation (The Hacker News, 2026-09-03).
The releases are unco-ordinated by the researcher's own account, and the reason they give matters for timeline planning rather than attribution. The Hacker News reports the researcher claiming that Microsoft continues to ignore them and refuses to engage in "any sort of communication", and quotes them saying they "can't even report the bugs I find to their respective vendors because of the restrictions by Microsoft" (The Hacker News, 2026-09-03). The same reporting quotes them planning the timing of future drops: "Think I will start publishing bugs for third-parties in that window where Patch Tuesday isn't released yet" (The Hacker News, 2026-09-03). For a defender that means there is no embargo to wait out and no co-ordinated patch date, the gap between publication and a vendor fix is open-ended, and by the researcher's own stated intent the next drop is likelier to land in the days before a Patch Tuesday than after one.
Triage: these exploits ride a security agent's legitimate high-privilege routines, so the signal is not the agent acting with privilege, which it always does. What separates abuse is what the privileged action produces: a remediation or sandbox operation followed by a process spawning from an unexpected parent under a low-privileged user's session, a write into a system directory that the agent's normal cleanup does not target, or SAM access originating from the antivirus process tree rather than from a backup or credential-management workflow. Because the code is public and the researcher notes detections may already exist, an endpoint alert naming the agent's own remediation component is worth treating as an exploitation attempt rather than a product fault.
We are actively investigating these claims and advise customers to disable the Microsoft Office File Suspicious Macro Removal Windows policy setting
As of now the PoC works in a fully updated windows 11 25H2 / Windows Server 2025 with Crowdstrike Falcon – Phase 3 Optimal Protection with “Microsoft Office file malicious macro removal” setting.
Gen was recently made aware of a security vulnerability affecting a subset of Gen products, including Avast Antivirus, that could allow an attacker to elevate their system privileges. We immediately initiated our security response procedures and are actively developing a patch.