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CVE-2023-27351

7.5, high Known exploited Used in ransomware

PaperCut NG/MF Improper Authentication Vulnerability

NVD (opens in a new tab) CVE.org (opens in a new tab) CISA KEV catalogue (opens in a new tab)
CVSS
7.5, high high CVSS v3.1
EPSS, next 30 days
78% higher than 99.5% of scored CVEs
Exploitation
Confirmed in the wild
Published
20 Apr 20233 years ago

Known exploited

CISA added this to the Known Exploited Vulnerabilities Catalog on 20 Apr 2026 and links it to ransomware activity. US federal agencies had to remediate by 4 May 2026, a deadline that has passed.

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.

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.

Details

Vendor
PaperCut
Product
NG
Weakness
CWE-287 (opens in a new tab)
Status
Analyzed
Updated
1 Oct 2026
Assigner
zdi-disclosures@trendmicro.com

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

References 3

Advisories 2

Other references 1

The kind is read from NVD's tags where present and from the shape of the URL otherwise, so treat it as a hint.

Other PaperCut CVEs

Every PaperCut CVE we hold

Same vendor in what we hold, not a known link between the flaws.

  • CVE-2026-81578 PaperCut NG/MF Missing Authentication for Critical Function Vulnerability KEV EPSS 86% 9.8, critical
  • CVE-2026-82078 PaperCut NG/MF Unsafe Reflection Vulnerability KEV EPSS 64% 9.1, critical
  • CVE-2023-2533 PaperCut NG/MF Cross-Site Request Forgery (CSRF) Vulnerability KEV EPSS 29% 8.8, high
  • CVE-2023-27350 PaperCut MF/NG Improper Access Control Vulnerability KEV EPSS 100% 9.8, critical

Beyond this page

Is CVE-2023-27351 in your network?

This page tells you how dangerous CVE-2023-27351 is out there. Whether it sits on one of your devices, only a scan of your own network can tell. That is what our systems do, every day, for the companies we protect.

CVE-2023-27351 is in the CISA catalogue of exploited vulnerabilities: attackers are already exploiting it.

  • EXYS7600 OCELOT

    Find it before attackers do

    Ocelot scans your network on a schedule and reports every vulnerability it finds by its CVE identifier, with its CVSS score and how many of your hosts are affected. A finding like CVE-2023-27351 comes with the devices to patch.

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  • EXYS7950 KONDRA

    Detect it if it's exploited

    Until the patch is applied, Kondra monitors your network, events and endpoints in real time. It keeps an inventory of the software installed on every endpoint, and its anomaly detection rules flag what an attacker does once inside.

    Learn more about EXYS7950 KONDRA
Check your exposure

Assembled from the NVD 2.0 API, the CISA Known Exploited Vulnerabilities Catalog and FIRST EPSS. Scores are as of our last collection on 17 Oct 2026, not the live upstream state.