| CVE | CVE-2026-81578 |
| Vulnerability Name | PaperCut NG/MF Missing Authentication for Critical Function Vulnerability |
| CVSS Score / Version | 9.8 (Critical) / CVSS v3.1 |
| Updated | 2026-09-25 |
| CVSS Vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CVSS Prose | attack vector is network; attack complexity is low; privileges required is none; user interaction is none; scope is unchanged; confidentiality impact is high; integrity impact is high; availability impact is high. |
| Affected products | PaperCut NG/MF, PaperCut PaperCut MF, and PaperCut PaperCut NG |
| Exploitation status | Listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation. |
| Classified as | CWE-306 (Missing Authentication for Critical Function) |
| KEV listing | Added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-08-31. |
| Exploitation prediction (EPSS) | 4.48% probability of exploitation in the next 30 days (91% percentile) -- FIRST.org's EPSS model. |
| Federal remediation deadline | 2026-09-14 (CISA KEV, Binding Operational Directive). |
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.
Monitor PaperCut's web page for any future patch releases.