PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
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…
Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.
Exploitation probability EPSS · FIRST
Exploitation signals 4 / 5
- KEV catalog (CISA)31 Aug 2026
- Exploited in EUVD (ENISA)27 Aug 2026
- Used by ransomwareno
- EPSS above 10 %84.7%
- No account, over the networkyes
What to do
Fix
Apply the vendor’s fix as soon as it is available.
CISA guidance: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Meanwhile
Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.
Manufacturers (CRA)
Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained
Description ENISA EUVD
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
- 0 <24.1.10
- 25.0.0 <25.0.13
- 26.0.0 <26.0.5
Open source packages OSV
Affected libraries according to OSV, with fixed versions.
Timeline
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Exploitation reported (ENISA)
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Published
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Added to the KEV catalog
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CISA remediation due date
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EPSS peak: 85.6%
References
Other exploited vulnerabilities from the same vendor
- CVE-2026-82078PaperCut NG/MF Unsafe Reflection Vulnerability7.5 · Actively exploited
- CVE-2023-27351PaperCut NG/MF Improper Authentication Vulnerability8.6 · Background exploitation
- CVE-2023-2533PaperCut NG/MF Cross-Site Request Forgery (CSRF) Vulnerability6.0 · Background exploitation
- CVE-2023-27350PaperCut MF/NG Improper Access Control Vulnerability9.9 · Background exploitation