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

CVE-2026-82078 is rated critical with a CVSS v3.1 base score of 9.1 and affects PaperCut NG/MF. Per its scoring, it can be exploited over the network, without any user interaction. The scored impact on confidentiality, integrity and availability is the highest available. CISA added it to its Known Exploited Vulnerabilities catalog on 2026-08-31, which means exploitation in the wild has been observed.

Vulnerability description

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.

Severity breakdown

CVSS v3.1 9.1: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

  • Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Privileges required: High. Administrative-level privileges are needed.
  • User interaction: None. No action from any user is needed.
  • Scope: Changed. Impact reaches beyond the vulnerable component to other resources.
  • Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
  • Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
  • Availability impact: High. Total loss of availability; the component can be shut down.

Underlying weakness

CWE-470: Use of Externally-Controlled Input to Select Classes or Code

The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.

Affected products

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

References