CVE-2023-27351

PaperCut NG/MF Improper Authentication Vulnerability

High 8.2
Exploited: added to CISA KEV 20 Apr 2026
Used in ransomware campaigns

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.

Key facts

Published: 20 Apr 2023
Last changed: 1 Oct 2026
Assigned by: zdi
KEV added: 20 Apr 2026
KEV fix due: 4 May 2026
Used in ransomware: Yes, according to CISA
EPSS: 78.052% likely to be exploited in the next 30 days, higher than 99.581% of CVEs (scores for 15 Nov 2026)
SSVC (CISA): Exploitation: active; Automatable: yes; Technical impact: total

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

8.2CVSS 3.0, Highfrom the CNA (zdi)CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

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.CISA KEV required action

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Vendor	Product	Versions
PaperCut	NG	22.0.5 (Build 63914) (affected)