CTIPilot

PaperCut MF

product · product:papercut-mf

Coverage timeline
1
first 2026-08-29 → last 2026-08-29
Peak priority
critical
1 critical
Sources cited
6
6 hosts
Sections touched
1
deep-dive
Co-occurring entities
3
see Co-occurring entities below
ATT&CK techniques
11
pinned v19.2 · see below

ATT&CK techniques

11 techniques observed across 1 entry, derived from entry metadata and body evidence, never asserted without a published entry behind it · pinned to MITRE ATT&CK v19.2 · compare on the matrix · Navigator layer (JSON)

Initial Access TA0001

T1078.002Valid Accounts: Domain Accounts×1

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

T1190Exploit Public-Facing Application×1

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network. The weakness in the system can be a software bug, a temporary glitch, or a misconfiguration.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Execution TA0002

T1059.007Command and Scripting Interpreter: JavaScript×1

Adversaries may abuse various implementations of JavaScript for execution. JavaScript (JS) is a platform-independent scripting language (compiled just-in-time at runtime) commonly associated with scripts in webpages, though JS can be executed in runtime environments outside the browser.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Persistence TA0003

T1078.002Valid Accounts: Domain Accounts×1

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

T1136.002Create Account: Domain Account×1

Adversaries may create a domain account to maintain access to victim systems. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover user, administrator, and service accounts. With a sufficient level of access, the <code>net user /add /domain</code> command can be used to create a domain account.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Privilege Escalation TA0004

T1078.002Valid Accounts: Domain Accounts×1

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Stealth TA0005

T1070.004Indicator Removal: File Deletion×1

Adversaries may delete files left behind by the actions of their intrusion activity. Malware, tools, or other non-native files dropped or created on a system by an adversary (ex: Ingress Tool Transfer) may leave traces to indicate to what was done within a network and how. Removal of these files can occur during an intrusion, or as part of a post-intrusion process to minimize the adversary's footprint.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

T1078.002Valid Accounts: Domain Accounts×1

Adversaries may obtain and abuse credentials of a domain account as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Domain accounts are those managed by Active Directory Domain Services where access and permissions are configured across systems and services that are part of that domain. Domain accounts can cover users, administrators, and services.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Credential Access TA0006

T1003.001OS Credential Dumping: LSASS Memory×1

Adversaries may attempt to access credential material stored in the process memory of the Local Security Authority Subsystem Service (LSASS). After a user logs on, the system generates and stores a variety of credential materials in LSASS process memory. These credential materials can be harvested by an administrative user or SYSTEM and used to conduct Lateral Movement using Use Alternate Authentication Material.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

T1003.006OS Credential Dumping: DCSync×1

Adversaries may attempt to access credentials and other sensitive information by abusing a Windows Domain Controller's application programming interface (API) to simulate the replication process from a remote domain controller using a technique called DCSync.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Discovery TA0007

T1057Process Discovery×1

Adversaries may attempt to get information about running processes on a system. Information obtained could be used to gain an understanding of common software/applications running on systems within the network. Administrator or otherwise elevated access may provide better process details. Adversaries may use the information from Process Discovery during automated discovery to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

T1082System Information Discovery×1

An adversary may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture. Adversaries may use this information to shape follow-on behaviors, including whether or not the adversary fully infects the target and/or attempts specific actions. This behavior is distinct from Local Storage Discovery which is an adversary's discovery of local drive, disks and/or volumes.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Lateral Movement TA0008

T1550.002Use Alternate Authentication Material: Pass the Hash×1

Adversaries may “pass the hash” using stolen password hashes to move laterally within an environment, bypassing normal system access controls. Pass the hash (PtH) is a method of authenticating as a user without having access to the user's cleartext password. This method bypasses standard authentication steps that require a cleartext password, moving directly into the portion of the authentication that uses the password hash.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Command and Control TA0011

T1219Remote Access Tools×1

An adversary may use legitimate remote access tools to establish an interactive command and control channel within a network. Remote access tools create a session between two trusted hosts through a graphical interface, a command line interaction, a protocol tunnel via development or management software, or hardware-level access such as KVM (Keyboard, Video, Mouse) over IP solutions. Desktop support software (usually graphical interface) and remote management software (typically command line interface) allow a user to control a computer remotely as if they are a local user inheriting the user or software permissions. This software is commonly used for troubleshooting, software installation, and system management. Adversaries may similarly abuse response features included in EDR and other defensive tools that enable remote access.

Evidence: 2026-08-29/papercut-ng-mf-tapestry-request-confusion-preauth-rce · ATT&CK page ↗

Story timeline

  1. 2026-08-29CVE-2026-82078 / CVE-2026-81578, PaperCut NG/MF: an Apache Tapestry request-routing confusion chains an unauthenticated config rewrite to arbitrary code execution, exploited before a patch existed
    deep-divePaperCut ships an emergency patch for a pre-auth RCE chain already used against live customers, and a second emergency release after the first one was bypassed

Where this entity is cited

  • deep-dive1

Source distribution

  • advisories.ncsc.nl1 (17%)
  • cert.ssi.gouv.fr1 (17%)
  • greynoise.io1 (17%)
  • huntress.com1 (17%)
  • papercut.com1 (17%)
  • rapid7.com1 (17%)

Co-occurring entities

Derived: referenced by the same focused operational entries (weekly summaries and report roundups don't count); ×N counts the shared entries.

Entries about PaperCut MF (1)

2026-08-29 · view entry permalink →

CRITICALCVE-2026-81578 +1exploitedupdatedNATOB1

CVE-2026-82078 / CVE-2026-81578, PaperCut NG/MF: an Apache Tapestry request-routing confusion chains an unauthenticated config rewrite to arbitrary code execution, exploited before a patch existed

PaperCut has been hit before at this scale: in 2023, CVE-2023-27350, an unrelated authentication-bypass flaw in the same PaperCut NG/MF Application Server, was mass-exploited in the wild by multiple ransomware operators before a patch existed, a precedent Rapid7's own incident-response team cites directly when framing why this new chain demands the same urgency (Rapid7, 2026-08-28). Three years later, PaperCut disclosed on 27 August 2026 that it was investigating active exploitation of a new, unrelated flaw in the same product line, again before any CVE, patch, or public technical detail existed, and again reconstructed from a real victim's own incident-response evidence: a university customer's security and DFIR team supplied the reproduction data that let PaperCut confirm and patch the bug (PaperCut Software, 2026-08-29).

PaperCut's Application Server runs on the Apache Tapestry web framework, whose "complex direct" request format lets a single HTTP request name one page to render and a different page's component to actually execute. PaperCut's own authorization check validates only the page selected for rendering, not the component that runs behind it, so a request that asks Tapestry to render the public, unauthenticated Error, Exception, or Home page while invoking the administrative ConfigEditor or UserList component bypasses authentication entirely (Rapid7, 2026-08-28). Through three such POST requests, /app?service=direct/1/Error/ConfigEditor/quickFindForm, .../ConfigEditor/$Form, and .../UserList/$QuickFind.$Form, an unauthenticated attacker rewrites four external card/ID lookup settings (user-lookup.db-driver, user-lookup.db-url, user-lookup.id-to-username-sql, user-lookup.enabled) that normally point PaperCut at an administrator-configured external card database (Rapid7, 2026-08-28). Redirected instead to an attacker-controlled JDBC target through PaperCut's bundled Apache Derby driver and its foreignViews feature, the connection reaches an attacker-controlled H2 database whose inline INIT statement creates a JavaScript-backed trigger; PaperCut's bundled Nashorn JavaScript engine then executes that trigger to launch an operating-system process, full remote code execution as the PaperCut server, triggered the moment the forged UserList search runs the malicious lookup (Rapid7, 2026-08-28). This is a two-CVE chain: CVE-2026-81578 (CWE-306, missing authentication) is the pre-auth entry that gains write access to the server configuration; CVE-2026-82078 (CWE-470, unsafe dynamic class loading) is the flaw that turns a reconfigured database connection into arbitrary Java bytecode execution once that write access is held (PaperCut Software, 2026-08-29).

PaperCut treats all versions of NG and MF as potentially affected. Huntress observed two live customer exploitations: one on 26 August lasting under two minutes against version 25.0.10.75465, and a second on 27 August against version 24.1.5.71847, before Emergency Patch Release 2 extended coverage to the v24 line (Huntress, 2026-08-28). In both cases the attacker ran base64-encoded discovery commands (whoami & ver, and separately whoami & ver & tasklist) via a dropped, OS-agnostic Java .class file that wrote its output to a temporary file and then deleted both that file and the server's own server.log (Huntress, 2026-08-28). Huntress's own proof-of-concept reproduced the full chain against a stock PaperCut NG install and observed the code execution surface as an observable charmap.exe process running as SYSTEM, spawned under the PaperCut Application Server's own pc-app.exe process (Huntress, 2026-08-28). PaperCut released an initial emergency patch for v25/v26 on 28 August, which a Home-page variant of the same request bypassed (Rapid7, 2026-08-28). Emergency Patch Release 2, published later the same day with hardening developed alongside Huntress and watchTowr, closed that bypass and extended coverage to v24, and was itself superseded on 1 September 2026 by Emergency Patch Release 3 (see Update below) (PaperCut Software, 2026-08-29). There is no fix for v23 and earlier (PaperCut's guidance for that line is to upgrade to a supported version) and Huntress estimates 47% of the roughly 2,500 PaperCut installations it tracks still run v23 or older (Huntress, 2026-08-28).

Detection, telemetry class first: alert on any child process spawned from pc-app.exe or the PaperCut Application Server's Java process, PaperCut never legitimately spawns a shell, cmd.exe, or a system-discovery utility such as charmap.exe, whoami, or tasklist from that lineage. Web-access logs for the PaperCut Application Server should be checked for POST requests to /app?service=direct/*/{Error,Exception,Home}/ConfigEditor/* or .../UserList/$QuickFind.$Form from unauthenticated or external sources; this URL shape is not a pattern ordinary PaperCut administration produces. Two log artifacts are near-unique indicators: a server.log line reading DB URL: jdbc:derby:memory:pwn, and a corresponding derby.log entry recording Derby booting an in-memory database directory whose name ends in the literal string pwn (Huntress, 2026-08-28). Both PaperCut and Huntress stress that these artifacts' absence does not clear a system, since the observed payloads delete their own server.log evidence after running (PaperCut Software, 2026-08-29). Triage: an unexpectedly truncated, gapped, or missing server.log on a PaperCut Application Server is not normal application behavior (legitimate log rotation does not delete mid-file) and is itself a high-confidence signal worth investigating even where no other artifact survives.

PaperCut Software security response team is investigating active exploitation of a vulnerability affecting PaperCut NG and PaperCut MF.

PaperCut Software

PaperCut's authorization check could trust the rendered page and miss the permissions required by the component behind it.

Huntress 2026-08-28

By selecting either the public Error page or Exception page for display, an attacker can bypass authentication while invoking administrative components belonging to ConfigEditor or UserList.

Rapid7 2026-08-28

47% of the approximately 2,500 PaperCut installations Huntress tracks are running v23 or older, for which no patch is currently available.

Huntress 2026-08-28

PaperCut has been targeted in the past; in 2023, CVE-2023-27350 was broadly exploited in the wild by multiple threat-actor groups, including ransomware operators.

Rapid7 2026-08-28

Emergency Patch (Release 3) has been released by our emergency response team and supersedes Release 2. You do not need to install previous patches, this patch is an accumulation of all emergency releases. This release addresses two known regressions and adds additional hardening and mitigation against potential attack chains.

As anticipated there is a second wave of attack on servers that are not fully patched and are publicly available.

PaperCut Software

compromise at least 440 instances of PaperCut MF/NG hosted by 395 identified victim organizations in 48 countries

GreyNoise observed the adversary achieved domain admin against only 12 victim organizations.

GreyNoise 2026-09-09
Updaterun 2026-09-03T0410Z-intelcvesactionsimmediate_actionsummarytechniquesevidencesourcing_notebody

PaperCut's Emergency Patch Release 3, published 1 September 2026, supersedes Release 2 and is cumulative, customers do not need to install the earlier releases first (PaperCut Software, 2026-09-02). Release 3 fixes two regressions Release 2 had itself introduced, broken SAML login flows, and lost support for legacy Microsoft SQL Server drivers used for external card lookup, and adds further, undisclosed hardening against the exploitation chain (PaperCut Software, 2026-09-02). PaperCut also confirms a second wave of attacks against servers that remain unpatched and internet-facing, involving "more sophisticated post-compromise behaviour" than what was observed in the first days of the incident (PaperCut Software, 2026-09-02). The vendor's own incident data, published 30 August as additional indicators of compromise, names a concrete follow-on chain from the original intrusion: after initial discovery commands, a PowerShell-delivered download installs a Windows service literally named "Remote Access Service" running SimpleService.exe, a SimpleHelp remote-access agent, as LocalSystem with auto-start, followed by a further download of AnyDesk; the bulletin does not state whether this specific chain recurred in the second wave or belongs only to the earlier intrusions it was published alongside (PaperCut Software, 2026-09-02). Mobility Print and Print Deploy server components are unaffected; Site Servers and secondary/print servers do need the same update as the primary Application Server (PaperCut Software, 2026-09-02).

Updaterun 2026-09-10T0410Z-intelsummarytechniquesactionssourcesevidencebody

GreyNoise's Global Observation Grid documents an AI-agent-orchestrated exploitation campaign against this chain beginning 31 August 2026, run by a likely Russian-speaking operator already tracked since July 2026 for attacks on Palo Alto, Ubiquiti, Citrix, SonicWall and Proxmox VE targets (GreyNoise, 2026-09-09). The operator built and tested both CVEs' exploits in a self-hosted PaperCut/Active Directory lab, sourced target lists via the Netlas.io scanning service, then deployed hundreds of AI agents, built on OpenAI's Codex harness paired with a DeepSeek model, to opportunistically "compromise at least 440 instances of PaperCut MF/NG hosted by 395 identified victim organizations in 48 countries" (GreyNoise, 2026-09-09). GreyNoise reports the adversary "went from an empty workspace to first achieving RCE against a real victim in just under four hours, first domain admin in an additional two hours, and once the full campaign launched, compromised at least 11 organizations in 26 seconds" (GreyNoise, 2026-09-09), with one US high school reaching full domain admin in seven minutes from initial access. Domain admin was ultimately reached against only twelve of the 395 compromised organizations, "GreyNoise observed the adversary achieved domain admin against only 12 victim organizations" (GreyNoise, 2026-09-09), via three paths: LSASS credential harvesting for pass-the-hash against the domain controller when the PaperCut host was domain-joined; the 2021 noPac flaws (CVE-2021-42278/CVE-2021-42287) where those remained unpatched; or directly adding a new account to Domain Admins when the PaperCut host itself ran on the domain controller or under a domain-admin service account. All three paths finished with a DCSync-based full NTDS.DIT credential dump; Cloudflare's WAF defeated the adversary against at least one targeted instance. This delta is reported by GreyNoise alone; a second independent source had not corroborated it as of this update.

vulnerability29 Aug 04:09Zmulti-sourceOpen finding ↗