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[ CVE-2023-27351 · Published 20 Apr 2023 ]

PaperCut NG/MF Improper Authentication Vulnerability

Exploited · CISA KEV CVSS 7.5 EPSS 78%No fix listed yet

[ Why it matters ]Priority signals

  • Exploited in the wild: on CISA's Known Exploited Vulnerabilities list since 2026-04-20
  • Known to be used in ransomware campaigns
  • EPSS: 78% chance of exploitation in the next 30 days (higher than 100% of CVEs)

[ Description ]Official description

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 SecurityRequestFilter class. The issue results from improper implementation of the authentication algorithm. An attacker can leverage this vulnerability to bypass authentication on the system. Was ZDI-CAN-19226.

CISA: PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class.

[ Fixes ]Fixes and patches

CISA required action (US federal deadline 4 May 2026): Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ References ]References