CVE-2023-27351
PaperCut NG/MF Improper Authentication Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 4 May 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS
- 78.05% probability · 100th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 20 April 2026 · due 4 May 2026 · used in ransomware campaigns
- Weakness
- CWE-287
- Affected
- papercut/papercut mf · papercut/papercut ng
- Source
- zdi-disclosures@trendmicro.com
EPSS 78.1% since 8 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
CISA notes
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. https://www.papercut.com/kb/Main/PO-1216-and-PO-1219 ; https://nvd.nist.gov/vuln/detail/CVE-2023-27351
References
- https://www.papercut.com/kb/Main/PO-1216-and-PO-1219Vendor Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-23-232/Third Party Advisory, VDB Entry
- https://www.papercut.com/kb/Main/PO-1216-and-PO-1219Vendor Advisory
- https://www.zerodayinitiative.com/advisories/ZDI-23-232/Third Party Advisory, VDB Entry
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27351US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.