What’s Vulnerable › Vulnerabilities

CVE-2026-81578: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability

• Severity: critical (CVSS 9.8 v3.1)
• Exploited in the wild: yes — in CISA KEV since 2026-08-31
• EPSS: 84.7% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-08-28 · updated 2026-09-14
• Weakness: CWE-305

Description

An improper access control vulnerability exists in the web management interface of PaperCut MF and PaperCut NG. Under specific conditions, unauthenticated remote requests targeting administrative functions can trigger backend actions prior to the completion of access validation checks. This allows an unauthenticated remote attacker to modify certain system configurations.

Affected products

• PaperCut MF: before 24.1.9; from 25.0.2 before 25.0.12; from 26.0.2 before 26.0.4 — fixed in 24.1.9, 25.0.12, 26.0.4
• PaperCut NG: before 24.1.9; from 25.0.2 before 25.0.12; from 26.0.2 before 26.0.4 — fixed in 24.1.9, 25.0.12, 26.0.4

How to fix

Upgrade to a fixed version: PaperCut MF 24.1.9, 25.0.12, 26.0.4; PaperCut NG 24.1.9, 25.0.12, 26.0.4. 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/security-bulletin-27-aug-2026-urgent-security-advisory/
• https://github.com/rapid7/metasploit-framework/pull/21842
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578

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