CVE-2026-82078: PaperCut NG/MF Unsafe Reflection Vulnerability

In short

PaperCut NG/MF has a weakness classified as unsafe reflection (CWE-470). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-08-31. NVD lists CVSS 4.0 at 9.4 CRITICAL.

What it is

“PaperCut NG/MF contains an unsafe reflection vulnerability that allows an attacker to manipulate system configuration parameters and execute arbitrary Java bytecode residing on the application classpath under the security context of the PaperCut server process. This vulnerability can be chained with CVE-2026-81578.” — CISA KEV, retrieved 2026-11-01

“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.” — NVD, retrieved 2026-11-01

Who is affected

PaperCut NG/MF. NVD lists the following versions as affected:

• Papercut Papercut Mf: before 24.1.9
• Papercut Papercut Mf: from 25.0.2 inclusive, before 25.0.12
• Papercut Papercut Mf: from 26.0.2 inclusive, before 26.0.4
• Papercut Papercut Ng: before 24.1.9
• Papercut Papercut Ng: from 25.0.2 inclusive, before 25.0.12
• Papercut Papercut Ng: from 26.0.2 inclusive, before 26.0.4

Exploitation status

CISA KEV added: 2026-08-31. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-09-14.

Scores

NVD CVSS 4.0: 9.4 CRITICAL; 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; source eb41dac7-0af8-4f84-9f6d-0272772514f4.

EPSS by FIRST: 63.05%; percentile 99.20; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-470.

Timeline

CISA required action

“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 KEV

What to do

• Confirm whether you run PaperCut NG/MF and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Patch, Vendor Advisory: https://www.papercut.com/kb/Main/security-bulletin-27-aug-2026-urgent-security-advisory/
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.