CVE-2023-27351 — Papercut Mf
HIGHCVE-2023-27351 is a high-severity (CVSS 7.5) Improper Authentication vulnerability in papercut papercut mf. It is in CISA's Known Exploited Vulnerabilities catalog (added 2026-04-20) and has been used in ransomware campaigns — treat it as actively exploited and patch now. A fix is available — see the affected versions and patch details below.
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.…
Exploitation Status
Actively exploited in the wild
- Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2026-04-20 — including use in ransomware campaigns. Federal agencies were required to remediate by 2026-05-04.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2023-27351.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2023-27351 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).
Where this sits among everything scored
Of 394,803 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.
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
papercut mfpapercutpapercut ngpapercutDetection & mitigation playbook
Vendor / applianceDetect
Inventory every papercut papercut mf deployment and check each version against the affected-products list above.
Fix
Apply the papercut papercut mf security patch or hotfix for CVE-2023-27351 on the affected version, following the vendor advisory for your exact build.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used. Alongside that, restrict the management interface to trusted networks and apply the vendor's recommended configuration mitigations.
How to detect CVE-2023-27351
A community-maintained Nuclei template exists for this CVE. You can scan for it directly:
nuclei -id cve-2023-27351 -u https://target- Template
- PaperCut NG - Authentication Bypass
- Severity
- high
- Impact
- Attackers can bypass authentication, gaining unauthorized access to the system and potentially executing malicious actions.
- Remediation
- Update to the latest version of PaperCut NG that addresses this issue or apply the security patch provided by the vendor.
Template by ProjectDiscovery nuclei-templates (daffainfo, jjcho), MIT licensed. View the full template. Scan only systems you are authorised to test.
Frequently Asked Questions
Is CVE-2023-27351 being exploited in your environment?
Detect and block the exploit chain at execution, on systems you cannot patch yet.