CVE-2026-81578
PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
PaperCut NG/MF
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.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 31 August 2026. US federal agencies were required to remediate it by 14 September 2026.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 1.6%, which is higher than 74.5% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Frequently asked questions
Is CVE-2026-81578 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2026-81578.
What does CVE-2026-81578 affect?
CVE-2026-81578 affects PaperCut NG/MF. 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.
How severe is CVE-2026-81578?
CVE-2026-81578 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 1.6%, higher than 74.5% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 14 September 2026.
How should organisations respond to CVE-2026-81578?
Apply the vendor patch for PaperCut NG/MF as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.