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CVE-2026-81578highunder attackCWE-305

PaperCut MF/NG: Authentication Bypass

86Vexday Risk Score

Patch now. It under exploitation confirmed by CISA and has a working public exploit.

ssvc Actcvss 8.8epss 0.8%
from disclosure to weapon1 days
Published on NVDAug 28
1st PoC+1d
metasploitAug 27
CISA KEVAug 28
exploitation probability
0.8%top 47% of all CVEs
observed exploitation
yesCISA + VulnCheck
3 public exploit(s)
Action required by CISAfederal deadline: 2026-09-14

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

In short

PaperCut's web management interface has a flaw that allows attackers to perform admin actions without logging in. By sending specially crafted requests, an attacker can bypass the login check and modify system settings.

Technical detail

An improper access control vulnerability in PaperCut MF/NG web management interface permits unauthenticated remote attackers to invoke administrative backend functions before authentication validation completes (CWE-305). The vulnerability enables unauthorized modification of system configurations through direct HTTP requests targeting admin endpoints.

Summary generated and translated by AI from the official description.
An improper access control vulnerability exists in the web management interface of PaperCut MF and PaperCut NG. Under specific conditions, unauthenticated remote requests targeting administrative functions can trigger backend actions prior to the completion of access validation checks. This allows an unauthenticated remote attacker to modify certain system configurations.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
Affected products
PaperCut · PaperCut MF/NG
public PoCs found — 3
githubgithub.com/yora1928/PaperCut-CVE-2026-81578-82078★ 2githubgithub.com/virologi-info/papercut-toolkit★ 1cve_referencegithub.com/rapid7/metasploit-framework/pull/21842unverified
⚠ Public resources, to assess the exposure of systems you control or are authorized to test. Test only with authorization.
References
https://github.com/rapid7/metasploit-framework/pull/21842https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/