CVE-2026-81578

PaperCut MF/NG: Authentication Bypass

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

PaperCut · PaperCut MF/NG

CVSS v4.0 CNA

8.8 HIGHCVSS: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 v3.1 NVD

9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

85.58% chance of exploitation in the next 30 days, 100th percentile

CISA KEV

added 2026-08-31

Nuclei

critical · CWE-306

Published

2026-08-28

Updated

2026-09-13

Proof-of-concept exploits (1)

• yora1928/PaperCut-CVE-2026-81578-820784★ · 2026-08-29

Nuclei templates (1)

• projectdiscovery/nuclei-templates/blob/main/http/cves/2026/CVE-2026-81578.yaml

Metasploit modules (1)

• rapid7/metasploit-framework/blob/master/modules/exploits/multi/http/papercut_ng_external_…

Security advisories

• https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory
• https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578
• rapid7/metasploit-framework/pull/21842

References

• CVE Record
• NVD entry

Related

• CVE-2026-15748
• CVE-2026-82078