CVE-2023-27351

PaperCut NG/MF Improper Authentication Vulnerability

Exploited in attacks Used by ransomware High 8.2 Attack chance: 78%

What it is

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.

CISA: PaperCut NG/MF contains an improper authentication vulnerability that could allow remote attackers to bypass authentication on affected installations via the SecurityRequestFilter class.

What to do

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

Deadline for US federal agencies: May 4, 2026

Added to the CISA list: April 20, 2026
Published: April 20, 2023
Severity: High 8.2 CVSS 3.0
Chance of attacks in the next 30 days (EPSS): 78% in the top 0.4% of all known vulnerabilities
Weakness: CWE-287
More details: NVD · CVE.org · CISA

All references (2)

More exploited flaws from PaperCut

Added	Vulnerability	Product	Severity	Attack chance
Aug 31, 2026	Missing Authentication for Critical FunctionCVE-2026-81578	NG/MF	High 8.8	84%
Aug 31, 2026	Unsafe ReflectionCVE-2026-82078	NG/MF	Critical 9.4	61%
Jul 28, 2025	Cross-Site Request Forgery (CSRF)CVE-2023-2533	NG/MF	High 8.4	29%
Apr 21, 2023	Improper Access ControlCVE-2023-27350used by ransomware	MF/NG	Critical 9.8	>99.9%

All of them →

Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.