Known exploited · PaperCut
CVE-2023-27351: PaperCut NG/MF Improper Authentication Vulnerability
What it is
PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class.
- Vendor
- PaperCut
- Product
- NG/MF
- Added to KEV
- April 20, 2026
- CISA due date
- May 4, 2026
- Ransomware use
- Known
- Weakness
- CWE-287: Improper Authentication
What CISA requires
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of NG/MF you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before May 4, 2026 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
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Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.