Actively exploited · Published Apr 20, 2023 · Assigned by zdi
CVE-2023-27351
High 8.2 Exploited Ransomware
In plain English
A high-severity improper authentication in NG from PaperCut. Attackers are actively exploiting it in the wild (listed by CISA on April 20, 2026). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 78.1% (higher than 99.6% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei, public proof-of-concept code. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA guidance
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Federal agencies must remediate by May 4, 2026.
Official 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 (as reported)
Weakness: CWE-287 · Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N