CVE-2026-81578: PaperCut NG/MF Missing Authentication for Critical Function Vulnerability
- Is it exploited?
Yes. CISA added it to the Known Exploited Vulnerabilities catalog on , 3 days after the CVE record was published.
- How likely is exploitation in the next 30 days?
- 83.7%
EPSS score, percentile 99.7 of all scored records
- How severe?
- 8.8 High
CVSS v4.0 base score, given by the CNA
- What should I do?
CISA deadline . Apply mitigations in accordance with vendor instructions … Full text
The CVE record links no vendor advisory, patch or mitigation.
- Which versions are affected?
Affected
- before 24.1.10
- from 25.0.0 to before 25.0.13
- from 26.0.0 to before 26.0.5
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
What to do
Required action, set by CISA
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 due date for this action: .
Advisories and patches
The CVE record links no vendor advisory, patch or mitigation.
Linked from CISA's catalog entry
- https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-81578
Affected products and versions
As listed in the CVE record.
| Status | Versions |
|---|---|
| Affected | before 24.1.10 |
| Affected | from 25.0.0 to before 25.0.13 |
| Affected | from 26.0.0 to before 26.0.5 |
Versions not listed are: unaffected.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
About this vulnerability
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.
Summary: CISA's KEV catalog, as of .
- CISA added CVE-2026-81578 to its Known Exploited Vulnerabilities (KEV) catalog on 31 Aug 2026.
- CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
- The due date CISA sets for the required action is 14 Sep 2026.
- The CVE record was published on 28 Aug 2026, 3 days before it was added to KEV.
- The CVE record carries a CVSS v4.0 base score of 8.8 (High), given by its CNA.
- FIRST's EPSS model puts the probability of exploitation in the next 30 days at 83.7% (percentile 99.7), as of 28 Oct 2026.
- CISA's SSVC assessment in the CVE record: exploitation active, automatable yes, technical impact partial.
Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of ; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of ; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of . About the data.
Description
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.
Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of . About the data.
Weakness
CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.
Timeline
| Date | Event |
|---|---|
| CVE record published | |
| Added to CISA KEV | |
| CVE record last updated | |
| CISA due date for the required action |
References
More exploited PaperCut vulnerabilities
- CVE-2026-82078: PaperCut NG/MF Unsafe Reflection Vulnerability
- CVE-2023-27351: PaperCut NG/MF Improper Authentication Vulnerability
- CVE-2023-2533: PaperCut NG/MF Cross-Site Request Forgery (CSRF) Vulnerability
- CVE-2023-27350: PaperCut MF/NG Improper Access Control Vulnerability