CVE-2026-81578
PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
Does this matter?
Known to be exploited in the wild (CISA KEV, CISA remediation deadline 14 September 2026). Treat as an emergency change: patch or isolate now, then hunt for prior compromise.
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
- 8.8 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 83.73% probability · 100th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Listed 31 August 2026 · due 14 September 2026
- Weakness
- CWE-305
- Affected
- papercut/papercut mf · papercut/papercut ng
- Source
- eb41dac7-0af8-4f84-9f6d-0272772514f4
EPSS moved from 4.5% on 24 September 2026 to 83.7% on 29 October 2026, peaking at 85.2% on 30 September 2026. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”.
CISA notes
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. https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/ ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2026-81578
References
- https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/Patch, Vendor Advisory
- https://github.com/rapid7/metasploit-framework/pull/21842Issue Tracking, Patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578Patch, Third Party Advisory, US Government Resource
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.