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Actively exploitedKnown ransomware use

CVE-2023-27350 PaperCut MF/NG Improper Access Control Vulnerability

PaperCut MF/NG contains an improper access control vulnerability within the SetupCompleted class that allows authentication bypass and code execution in the context of system.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment
  • CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 21 Apr 2023.
  • CISA lists it as known to be used in ransomware campaigns.
  • Rated Critical severity (CVSS 9.8, scored by Vendor).
  • Named in Cybergen threat actor reporting: LockBit.
  • It has been in the catalogue for 1,295 days. Systems still unpatched now have almost certainly been scanned for it.
The Vulnerability

What It Is

This vulnerability allows remote attackers to bypass authentication on affected installations of PaperCut NG 22.0.5 (Build 63914). Authentication is not required to exploit this vulnerability. The specific flaw exists within the SetupCompleted class. The issue results from improper access control. An attacker can leverage this vulnerability to bypass authentication and execute arbitrary code in the context of SYSTEM. Was ZDI-CAN-18987.

Affected Versions

ProductVersions
PaperCut NG22.0.5 (Build 63914)

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

  1. 1

    Find it

    Search your asset inventory and external attack surface for PaperCut MF/NG. Include cloud images, appliances and anything a supplier runs for you.

    Attack Surface Management
  2. 2

    Fix it

    Apply updates per vendor instructions.

    Vulnerability Management
  3. 3

    Hunt for compromise

    If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.

    Incident Response
  4. 4

    Prove it is fixed

    Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.

    Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 12 May 2023 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited PaperCut Flaws

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CVE-2026-82078PaperCut NG/MF Unsafe Reflection VulnerabilityAdded 31 Aug 2026CVE-2026-81578PaperCut NG/MF Missing Authentication for Critical Function VulnerabilityAdded 31 Aug 2026CVE-2023-27351 · RansomwarePaperCut NG/MF Improper Authentication VulnerabilityAdded 20 Apr 2026CVE-2023-2533PaperCut NG/MF Cross-Site Request Forgery (CSRF) VulnerabilityAdded 28 Jul 2025

All 5 exploited PaperCut vulnerabilities

Not Sure If You Are Exposed?

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Evidence

Sources

  1. CISA Known Exploited Vulnerabilities catalogue
  2. NVD: CVE-2023-27350
  3. CVE record: CVE-2023-27350
  4. FIRST EPSS
  5. papercut.com/kb/Main/PO-1216-and-PO-1219
  6. zerodayinitiative.com/advisories/ZDI-23-233/
  7. packetstormsecurity.com/files/171982/PaperCut-MF-NG-Authentication-Bypass-Remote-Code-Execution.html
  8. packetstormsecurity.com/files/172022/PaperCut-NG-MG-22.0.4-Authentication-Bypass.html
  9. news.sophos.com/en-us/2023/04/27/increased-exploitation-of-papercut-drawing-blood-around-the-interne
  10. packetstormsecurity.com/files/172512/PaperCut-NG-MG-22.0.4-Remote-Code-Execution.html
  11. packetstormsecurity.com/files/172780/PaperCut-PaperCutNG-Authentication-Bypass.html