What is CVE-2026-81578?
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.
The record classifies CVE-2026-81578 under weakness class CWE-305. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 47 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 9.8 — CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS v4.0 base score
- 8.8
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 - EPSS (FIRST)
- 85.5% probability of exploitation in the next 30 days, higher than 99.7% of all scored CVEs
- CISA KEV
- Listed since 2026-08-31, federal remediation deadline 2026-09-14
- Threadlinqs priority
- 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- Published
- 2026-08-28, last modified 2026-09-13
Is CVE-2026-81578 being exploited?
CISA added CVE-2026-81578 to the Known Exploited Vulnerabilities catalog on 2026-08-31, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-09-14 under BOD 22-01. Weaponised exploit code for CVE-2026-81578 is publicly available. 2 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (http/cves/2026/CVE-2026-81578.yaml). It currently carries a trending score of 74 in the Threadlinqs vulnerability feed.
- yora1928/PaperCut-CVE-2026-81578-82078 (github)
- virologi-info/papercut-toolkit (github)
Affected products and versions
- PaperCut: MF/NG
How to fix CVE-2026-81578
The record marks a vendor fix as available for CVE-2026-81578. Patch reference: https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/. Vendor advisory: https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/. Because CVE-2026-81578 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-09-14. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2026-81578
1 tracked threat in the Threadlinqs corpus references CVE-2026-81578, either in the campaign’s CVE list or as an indicator on the campaign record.
- PaperCut NG/MF Chained Zero-Day RCE (CVE-2026-82078 & CVE-2026-81578) Under Active Exploitation — CRITICAL · 2026-08-28
Sources
Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.