How severe is CVE-2023-27351?

CVE-2023-27351 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-27351?

Affected package information for CVE-2023-27351 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2023-27351?

No fixed version has been published for CVE-2023-27351 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2023-27351 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-27351 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-27351?

CVE-2023-27351 has an EPSS (Exploit Prediction Scoring System) score of 83.3%, placing it in the 99th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2023-27351 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2023-27351 (PaperCut NG/MF Improper Authentication Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-04-20. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-05-04. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. This CVE has been used in known ransomware campaigns. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2023-27351?

CVE-2023-27351 is classified as Improper Authentication (CWE-287). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2023-27351?

CVE-2023-27351 affects papercut papercut mf; papercut papercut ng. Check the affected-products list on this page against your deployed version to confirm exposure.

Is there exploit tooling available for CVE-2023-27351?

A Nuclei detection template exists for CVE-2023-27351, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2023-27351 published, and has it been updated?

CVE-2023-27351 was published on April 20, 2023 and was last updated on April 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2023-27351: Papercut Mf Improper Authentication (High 7.5)

EPSS Exploitation Probability

via FIRST.org ↗

83.3%probability of exploitation in next 30 days

Very High Risk99th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

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

2 products · 6 configurations

Application

papercut mfpapercut

≥ 22.0.0 && < 22.0.9

range

Application

papercut ngpapercut

≥ 22.0.0 && < 22.0.9

range

Frequently Asked Questions

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.

O3 Security · Impact-Aware SCA

Is CVE-2023-27351 in your stack?

O3 detects CVE-2023-27351 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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