CVE-2026-81578
KEV: known exploited SSVC: activePaperCut MF/NG: Authentication Bypass
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
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
Attack conditions and impact
Derived from the NVD CVSS 3.1 vectorThis vulnerability may be exploitable over the internet without authentication or user interaction.
| Metric | Value | Meaning |
|---|---|---|
| Attack vector AV | N | Network |
| Attack complexity AC | L | Low (easy) |
| Privileges required PR | N | None |
| User interaction UI | N | None |
| Scope S | U | Unchanged |
| Confidentiality C | H | High |
| Integrity I | H | High |
| Availability A | H | High |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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.
CISA KEV entry
PaperCut NG/MF Missing Authentication for Critical Function Vulnerability — PaperCut / NG/MF
PaperCut NG/MF contains a missing authentication for critical function vulnerability which allows an unauthenticated remote attacker to modify certain system configurations. This vulnerability can be chained with CVE-2026-82078.
Required action: 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
CVSS assessments
| Provider | Version | Score | Vector |
|---|---|---|---|
| NVD / eb41dac7-0af8-4f84-9f6d-0272772514f4 (Secondary) | 4.0 | 8.8 HIGH | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
| NVD / [email protected] (Primary) | 3.1 | 9.8 CRITICAL | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| CNA / PaperCut | 4.0 | 8.8 HIGH | 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 and packages
CNA (CVE.org)
| Vendor | Product | Versions |
|---|---|---|
| PaperCut | PaperCut MF/NG | affected: 0 … < 24.1.10 affected: 25.0.0 … < 25.0.13 affected: 26.0.0 … < 26.0.5 default: unaffected |
NVD CPE (6)
Show CPE list
| Vendor | Product | Range | CPE |
|---|---|---|---|
| papercut | papercut_mf | < 24.1.9 | cpe:2.3:a:papercut:papercut_mf:*:*:*:*:*:*:*:* |
| papercut | papercut_mf | >= 25.0.2, < 25.0.12 | cpe:2.3:a:papercut:papercut_mf:*:*:*:*:*:*:*:* |
| papercut | papercut_mf | >= 26.0.2, < 26.0.4 | cpe:2.3:a:papercut:papercut_mf:*:*:*:*:*:*:*:* |
| papercut | papercut_ng | < 24.1.9 | cpe:2.3:a:papercut:papercut_ng:*:*:*:*:*:*:*:* |
| papercut | papercut_ng | >= 25.0.2, < 25.0.12 | cpe:2.3:a:papercut:papercut_ng:*:*:*:*:*:*:*:* |
| papercut | papercut_ng | >= 26.0.2, < 26.0.4 | cpe:2.3:a:papercut:papercut_ng:*:*:*:*:*:*:*:* |
Linux distribution status
References (3)
- https://github.com/rapid7/metasploit-framework/pull/21842 NVD, ADP CISA-ADP Issue TrackingPatchexploit
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578 NVD, ADP CISA-ADP PatchThird Party AdvisoryUS Government Resourcegovernment-resource
- https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/ NVD, CNA PatchVendor Advisory