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CVE-2023-27351

PaperCut — PaperCut NG/MF Improper Authentication Vulnerability

PaperCut · CWE-287 — Improper authentication · in CISA KEV since 2026-04-20

CISA federal deadline · Overdue by 6 monthsRansomwareCISA KEVActively Exploited
87

EVRS 87 of 100 Immediate

Patch Immediately

Rank 301 of 2,960 tracked

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Why it scores 87

Evidence available: 6 of 7 signals

Listed in the CISA KEV catalog, and associated with known ransomware campaigns.

  • CISA KEVApplied
  • RansomwareApplied
  • Vendor exploitationDid not apply
  • EPSSApplied
  • Microsoft Exploitability IndexNot applicable
  • Pre-patch disclosureNo data
  • KEV recencyDid not apply
  • CVSSApplied

The band answers “how soon”, not “how bad”. No data for: Pre-patch disclosure. Why some signals show no data

Fix

Patch or fixed version identified

CISA required action

Fixed in

papercut mf: update to 20.1.7 or later | papercut mf: update to 21.2.11 or later | papercut mf: update to 22.0.9 or later | papercut ng: update to 20.1.7 or later | papercut ng: update to 21.2.11 or later | papercut ng: update to 22.0.9 or later

Affected versions

  • papercut mf>= 15.0 < 20.1.7>= 21.0.0 < 21.2.11>= 22.0.0 < 22.0.9
  • papercut ng>= 15.0 < 20.1.7>= 21.0.0 < 21.2.11>= 22.0.0 < 22.0.9

Remediation

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Fixed versions from NVD.

Evidence

Each value with its source
MeasureValueSource
CVSS base scoreHow severe the flaw is in itself. It does not say how likely an attack is. 7.5 NVD
FIRST EPSSFIRST's estimate of the chance this is exploited in the next 30 days, and how that ranks against all CVEs. 0.781 (99.58th pctl) FIRST EPSS
Actively exploitedWhether a source of record has confirmed attacks using it in the wild. Confirmed CISA KEV
Ransomware campaign useWhether CISA has seen ransomware operators use it. Known CISA KEV
CISA remediation deadlineThe date US federal agencies must have fixed or mitigated it. 2026-05-04 · CISA federal deadline · Overdue by 6 months CISA KEV
Public exploit moduleA module existing is not the same as active exploitation. None known Metasploit
EUVD cross-referenceENISA's record: CVSS 8.2 (v3.0), assigned by zdi. Listed ENISA EUVD

Description

NVD

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.

What CISA says to do