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CVE-2023-27351

PaperCut NG/MF Improper Authentication

7.5 HIGHActively exploited (CISA KEV)Used in ransomwareEPSS 78.1%
  1. Published20 Apr 2023
  2. Added to CISA KEV20 Apr 2026
  3. Remediation due4 May 2026
Actively exploited (CISA KEV)

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

Added to KEV: 20 Apr 2026Federal remediation due: 4 May 2026Used in ransomware

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityNone
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected products

Papercut Mf≥ 15.0 < 20.1.7 · ≥ 21.0.0 < 21.2.11 · ≥ 22.0.0 < 22.0.9
Papercut Ng≥ 15.0 < 20.1.7 · ≥ 21.0.0 < 21.2.11 · ≥ 22.0.0 < 22.0.9

Remediation

Fixed in
Papercut Mf≥ 20.1.7
Papercut Ng≥ 20.1.7

References

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Frequently asked

Is CVE-2023-27351 being actively exploited?

Yes. CVE-2023-27351 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 20 Apr 2026. It has been used in ransomware campaigns.

How severe is CVE-2023-27351?

CVE-2023-27351 has a CVSS 3.1 base score of 7.5, rated high. EPSS estimates a 78.1% probability of exploitation.

Which products are affected by CVE-2023-27351?

Affected products include Papercut Mf, Papercut Ng.

How do I fix CVE-2023-27351?

Upgrade affected software to a fixed version, for example Papercut Mf 20.1.7, Papercut Ng 20.1.7 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2023-27351 against the real software inventory on every managed device, every day. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, Secuno flags any affected asset as top-priority automatically. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.