PaperCut · NG/MF · PaperCut NG/MF Unsafe Reflection Vulnerability
Verdict
Patch on your normal cycle · actively exploited, not reachable unauthenticated from the internet, and in the top 25% of CVEs by near-term exploitation probability
Added to CISA KEV 2026-08-31 · exploited in the wild for 27 days
CVSS 9.4 CRITICAL. The score is a summary; these three components are the part that decides whether something scanning the internet can use it.
| Attack vector | networkreachable over the network, with no local access needed |
|---|---|
| Privileges required | highneeds elevated privileges before it can be used |
| User interaction | nonecan be triggered with nobody interacting with the page or request |
| Base vector | CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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 |
| Weakness | CWE-470 |
This describes the vulnerability. It says nothing about whether your systems run it.
EPSS puts the probability of exploitation in the next 30 days at 0.0384, which places it in the top 25% of all tracked CVEs. The percentile is the more useful half: 0.18 in absolute terms sounds low until you know most of the internet-facing software in the world scores under that.
| EPSS probability | 0.0384 |
|---|---|
| Percentile | 0.898 — top 25% |
| Added to KEV | 2026-08-31 |
|---|---|
| Days exploited | 27 |
| Federal remediation due | not set |
| Ransomware use | no known ransomware campaign use |
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.
An unsafe dynamic class loading vulnerability exists in the database connection utilities of PaperCut MF and PaperCut NG. The application instantiates database driver classes based on configurable driver names without validating against an allowlist of approved drivers. If an attacker can manipulate system configuration parameters, this enables the execution of arbitrary Java bytecode residing on the application classpath under the security context of the PaperCut server process.