Quick answer
Direct answer
Risk scores
| CVSS metric | What it means |
|---|---|
| Attack vector (AV:N) | Network: reachable remotely |
| Attack complexity (AC:L) | Low complexity |
| Attack requirements (AT:N) | No attack requirements |
| Privileges required (PR:N) | No privileges required |
| User interaction (UI:N) | No user interaction |
| Confidentiality (VC:L) | Low confidentiality impact |
| Integrity (VI:H) | High integrity impact |
| Availability (VA:L) | Low availability impact |
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:X
CISA required action
About PaperCut NG/MF
CVE-2026-81578 affects PaperCut NG/MF, a product from PaperCut. Before acting, confirm where PaperCut NG/MF runs in your estate, who owns it and whether it is reachable from the internet, because exposure decides real risk more than the score alone.
What the flaw is
In plain terms: 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.
Based on its CVSS vector, the flaw can be reached over the network, needs no login, and needs no user interaction. It is listed in the CISA Known Exploited Vulnerabilities catalog, so treat it as an active threat and patch immediately.
Affected versions and timeline
| Field | Detail |
|---|---|
| Product | PaperCut NG/MF |
| Affected versions | Papercut Mf before 24.1.9; Papercut Mf from 25.0.2 before 25.0.12; Papercut Mf from 26.0.2 before 26.0.4; Papercut Ng before 24.1.9; Papercut Ng from 25.0.2 before 25.0.12; Papercut Ng from 26.0.2 before 26.0.4 |
| Published | Aug 28, 2026 |
| Last modified | Sep 14, 2026 |
| Added to CISA KEV | Aug 31, 2026 |
| Assigning CNA | eb41dac7-0af8-4f84-9f6d-0272772514f4 |
How to detect it
- Inventory every instance of PaperCut NG/MF and record the running version against the affected range above.
- Check external attack surface scans for internet facing instances of the component.
- Review logs on affected systems for unusual requests, errors or new processes around the vulnerable function.
- Confirm with an authenticated vulnerability scan once your scanner has a check for this CVE.
How to fix it
- Apply the fixed version of PaperCut NG/MF named in the vendor advisory.
- If patching must wait, restrict network access to the affected service and put it behind authentication or a web application firewall rule.
- Rescan after the change to prove the exposure is gone, then close the ticket.
CTEM action plan
| CTEM stage | What to do for this CVE |
|---|---|
| Scope | Add every business service that depends on PaperCut NG/MF to the current CTEM cycle. |
| Discover | Find all instances, including shadow and cloud deployments, and record versions and exposure. |
| Prioritize | Known exploited, so top priority. |
| Validate | Confirm the flaw is reachable and exploitable in your environment and that compensating controls work. |
| Mobilize | Assign the fix to the asset owner with a due date matched to the priority, then verify closure. |
CWE References
Technical References
Frequently asked questions
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