What is CVE-2023-27351?

CVE-2023-27351 is a high-severity vulnerability in Papercut Ng, classified under Improper Authentication. CVSS score: 7.5/10. Published 2023-04-20.

How severe is CVE-2023-27351?

High severity. CVSS v3 base score is 7.5 out of 10.

Is CVE-2023-27351 known to be exploited?

Yes. CVE-2023-27351 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-20), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.

Auth bypass in Papercut Ng

CVE-2023-27351

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.

Vulnerability class: Broken Authentication

Published 2023-04-20 · last modified 2026-10-01.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.781 (99.6th percentile), scored 2026-10-18.

High probability of exploitation in the next 30 days — patch promptly. 100th percentile — 99.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.781 · newest: 0.781 · change: 0.000

Affected products

Papercut Ng — versions 22.0.5 (Build 63914)
Papercut Mf
Papercut Ng

Weakness classification (CWE)

CWE-287 — Improper Authentication

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2026-04-20. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2026-05-04.

Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Known ransomware campaign use: yes.

Public proof-of-concept exploits

References

www.papercut.com/kb/Main/PO-1216-and-PO-1219 (Vendor Advisory)
www.zerodayinitiative.com/advisories/ZDI-23-232/ (VDB Entry, Third Party Advisory)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2023-27351?: CVE-2023-27351 is a high-severity vulnerability in Papercut Ng, classified under Improper Authentication. CVSS score: 7.5/10. Published 2023-04-20.
How severe is CVE-2023-27351?: High severity. CVSS v3 base score is 7.5 out of 10.
Is CVE-2023-27351 known to be exploited?: Yes. CVE-2023-27351 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2026-04-20), indicating it is being actively exploited. 2 public proof-of-concept repositories are indexed.