CVE-2026-81578
KEVPaperCut NG/MF Missing Authentication for Critical Function Vulnerability
Description
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.
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.
CVSS 4.0 vector
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:XPublishedAug 28, 2026
Last modifiedSep 14, 2026
Added to KEVAug 31, 2026
Remediation dueSep 14, 2026
References
- papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/PatchVendor Advisory
- github.com/rapid7/metasploit-framework/pull/21842Issue TrackingPatch
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-81578PatchThird Party Advisory
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82
Risk assessment · Critical
Actively exploited. Patch immediately.
- Exploitation
- Confirmed in the wild (CISA KEV)
- Federal remediation deadline
- Overdue by 43 days
- CVSS
- 8.8 HIGH
- EPSS (30-day exploit probability)
- 83.7% · top 1% of all CVEs
- Weakness
- CWE-305
- Attack vector
- Network, remotely reachable
- Preconditions
- No privileges and no user interaction
Recommended actions
- 1.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.
- 2.Treat as emergency change: patch or isolate internet-facing instances first.
- 3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
- 4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
Assessment is derived automatically from the live signals above; verify against your own asset inventory.