CVEs / CVE-2026-81578
CVE-2026-81578: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
- Known exploited in the CISA KEV catalog since 31 Aug 2026
- critical 9.8 CVSS 3.1 (NVD)
- EPSS 84.7% chance of exploitation in the next 30 days, higher than 99% of CVEs (30 Oct 2026)
- Last changed at its sources
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Summary
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.
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.
Affected and fixed versions
| Product | Affected | Fixed in |
|---|---|---|
| PaperCut PaperCut MF/NG | before 24.1.10 | 24.1.10 |
| PaperCut PaperCut MF/NG | from 25.0.0, before 25.0.13 | 25.0.13 |
| PaperCut PaperCut MF/NG | from 26.0.0, before 26.0.5 | 26.0.5 |
Exploitation
| In CISA KEV since | 31 Aug 2026 |
|---|---|
| Due date for US federal agencies | 14 Sep 2026 |
| Used in ransomware campaigns | Unknown |
| 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. |
Severity
| CVSS 3.1 | 9.8 criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HScored by NVD |
|---|---|
| Weakness | CWE-305 |
References
- CVE-2026-81578 on NVD
- CVE-2026-81578 in the CISA KEV catalog
- https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/ (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk (cited by CISA)
- https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/ Patch, Vendor Advisory
- https://github.com/rapid7/metasploit-framework/pull/21842 Issue Tracking, Patch
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578 Patch, Third Party Advisory, US Government Resource
Sources
Exploitation status from the CISA Known Exploited Vulnerabilities catalog. EPSS scores from FIRST. Descriptions, severity and references from the National Vulnerability Database. Open-source package versions from OSV (CC-BY 4.0). Text is shown as each source states it; Stackurity does not edit it. Check the vendor's advisory before acting.
This product uses data from the NVD API but is not endorsed or certified by the NVD.