PaperCut NG/MF Improper Authentication Vulnerability (CVE-2023-27351)
Severity: high · Patch status: unknown · Since 2026-04-20 · CVE-2023-27351
PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class. CISA added CVE-2023-27351 to its Known Exploited Vulnerabilities catalog on Apr 20, 2026, which means attackers are exploiting it in the wild. CISA reports known use in ransomware campaigns.
What to do
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- US federal agencies must remediate by May 4, 2026 (BOD 22-01); treat that as the outer limit.
Sources
All live incidents on Threat Watch
