PaperCut NG/MF Unsafe Reflection
CVE-2026-82078 is a critical-severity use of externally-controlled input to select classes or code vulnerability in PaperCut MF/NG from PaperCut, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an attacker with administrator privileges, without any action from a user. The record lists versions 24.1.10, 25.0.13, 26.0.5 as the first without the flaw, so updating PaperCut MF/NG to one of those releases or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on August 31, 2026, which means attacks have been observed in the wild.
Attackers are already exploiting this vulnerability, according to CISA.
What to do
- Update PaperCut MF/NG to 24.1.10 or 25.0.13 or 26.0.5, whichever matches your release line, or a later version.
- Update Papercut Mf to 24.1.9 or 25.0.12 or 26.0.4, whichever matches your release line, or a later version.
- Update Papercut Ng to 24.1.9 or 25.0.12 or 26.0.4, whichever matches your release line, or a later version.
- CISA's 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.
- Read the advisory on papercut.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| PaperCut | PaperCut MF/NG | before 24.1.10; 25.0.0 up to, but not including, 25.0.13; 26.0.0 up to, but not including, 26.0.5 | 24.1.10, 25.0.13, 26.0.5 |
| Papercut | Papercut Mf | before 24.1.9; 25.0.2 up to, but not including, 25.0.12; 26.0.2 up to, but not including, 26.0.4 | 24.1.9, 25.0.12, 26.0.4 |
| Papercut | Papercut Ng | before 24.1.9; 25.0.2 up to, but not including, 25.0.12; 26.0.2 up to, but not including, 26.0.4 | 24.1.9, 25.0.12, 26.0.4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- HighAdministrator-level access is required first.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.4 | Critical | CNA |
| CVSS 3.1 | 9.1 | Critical | NVD |
Official 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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: 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.
How developers prevent this class of flaw
- Refactor your code to avoid using reflection.
- Do not use user-controlled inputs to select and load classes or code.
- Apply strict input validation by using allowlists or indirect selection to ensure that the user is only selecting allowable classes or code.
More Use of Externally-Controlled Input to Select Classes or Code vulnerabilities (CWE-470)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
- Added to CISA's Known Exploited Vulnerabilities catalogue.
- Record last changed materially (score, affected products, status or references).
- Deadline for US federal agencies to remediate, set by CISA.
References
Patches and release notes
- github.com/rapid7/metasploit-framework/pull/21842Issue Tracking
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-82078Third Party Advisory, US Government Resource
Our coverage
Other vulnerabilities in PaperCut MF/NG
- 9.8 Critical severity
Recent Use of Externally-Controlled Input to Select Classes or Code vulnerabilities
- 8.8 High severity
- 7.5 High severity
- 7.2 High severity
- 9.8 Critical severity
- 7.2 High severity
- 8.8 High severity
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