Known exploited vulnerability
CVE-2023-27351
The short answer
CVE-2023-27351 affects PaperCut NG and is rated high (CVSS 7.5). CISA added it to the Known Exploited Vulnerabilities catalog on 2026-04-20: attackers are using it, so patch it first.
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.
Weakness: CWE-287.
Severity
7.5 high
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Exploited (CISA KEV)
Yes, since Apr 20, 2026
Federal due date May 4, 2026
EPSS, next 30 days
78%
Higher than 100% of scored CVEs
How it can be exploited
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- None
- Availability impact
- None
What CISA says 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.
Affected products
NG. NVD's record lists the exact affected versions.
References
- www.papercut.com/kb/Main/PO-1216-and-PO-1219 Vendor Advisory
- www.zerodayinitiative.com/advisories/ZDI-23-232/ Third Party AdvisoryVDB Entry
- www.papercut.com/kb/Main/PO-1216-and-PO-1219 Vendor Advisory
- www.zerodayinitiative.com/advisories/ZDI-23-232/ Third Party AdvisoryVDB Entry
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-27351 US Government Resource
Questions
Is CVE-2023-27351 being exploited?
Yes. CISA added CVE-2023-27351 to its Known Exploited Vulnerabilities catalog on 2026-04-20, with a federal remediation due date of 2026-05-04. CISA lists it as used in ransomware campaigns.
How do I fix CVE-2023-27351?
CISA's 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.
From NVD, CISA KEV, FIRST EPSS and OSV.dev, checked . Status on NVD: Analyzed. The description is NVD's text, quoted as published.
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