What’s Vulnerable › Vulnerabilities

CVE-2023-27351: PaperCut NG/MF Improper Authentication Vulnerability

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-04-20
• EPSS: 78.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-04-20 · updated 2026-10-01
• Weakness: CWE-287

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.

Affected products

• PaperCut MF: from 15.0 before 20.1.7; from 21.0.0 before 21.2.11; from 22.0.0 before 22.0.9 — fixed in 20.1.7, 21.2.11, 22.0.9
• PaperCut NG: from 15.0 before 20.1.7; from 21.0.0 before 21.2.11; from 22.0.0 before 22.0.9 — fixed in 20.1.7, 21.2.11, 22.0.9

How to fix

Upgrade to a fixed version: PaperCut MF 20.1.7, 21.2.11, 22.0.9; PaperCut NG 20.1.7, 21.2.11, 22.0.9. Check the vendor advisory for mitigations.

In the news

• Death By A Thousand PaperCuts (PaperCut Pre-Auth RCE Chain and Patch Bypasses WT-2026-0141-0144/CVE-2026-82077/CVE-2026-82078/CVE-2026-81578)

References

• https://www.papercut.com/kb/Main/PO-1216-and-PO-1219
• https://www.zerodayinitiative.com/advisories/ZDI-23-232/
• https://www.papercut.com/kb/Main/PO-1216-and-PO-1219
• https://www.zerodayinitiative.com/advisories/ZDI-23-232/
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27351

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