CVE-2026-81578

PaperCut NG/MF: Missing Authentication for Critical Function

As of , CVE-2026-81578 in PaperCut NG/MF is on CISA's list of exploited vulnerabilities: CISA listed it on . Our patch-first group: Patch this week.

Exploited
Yes: CISA listed it on 31 August 2026
US federal deadline
14 September 202614 days after CISA listed it. US federal civilian agencies must fix it by then.
Used in ransomware campaigns
Not known to CISA
EPSS score
0.85Higher than 99% of the CVEs EPSS scores. EPSS estimates the chance of exploitation activity in the next 30 days.
Public exploit
1 Metasploit module
Fix
Vendor advice: www.papercut.comLinks below, from CISA's entry.

What CISA says to do

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.

CISA's required action

What the flaw is

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.

CISA's 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.

The CVE record's description, from PaperCut

CVE published
28 August 2026
Assigned by
PaperCut
CVSS
8.8 High (CVSS 4.0, from the CNA)
CWE-305
Authentication Bypass by Primary Weakness
CWE-306
Missing Authentication for Critical Function
CISA SSVC, exploitation
active
CISA SSVC, automatable
yes
CISA SSVC, technical impact
partial

Timeline

  1. The CVE record was published.
  2. CISA added it to its list of exploited vulnerabilities.
  3. The US federal deadline to fix it.

Public exploits

Facts from Metasploit's module list and Exploit-DB's index; we never copy exploit code.

  • Metasploit: PaperCut NG/MF Unauthenticated RCE (CVE-2026-81578 + CVE-2026-82078)exploit module, rank excellent

NG/MF: other exploited entries

VulnerabilityProductOur groupListedDeadlineEPSS
CVE-2023-27351Improper AuthenticationPaperCut NG/MFPatch nowRansomware use, listed within a year0.78
CVE-2026-82078Unsafe ReflectionPaperCut NG/MFPatch this weekMetasploit module; EPSS 0.610.61
CVE-2023-2533Cross-Site Request Forgery (CSRF)PaperCut NG/MFPatch soon0.29

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