URGENT Security Advisory: PaperCut NG/MF Security Bulletin (27 Aug 2026)

URGENT Security Advisory

PaperCut Software security response team is investigating active exploitation of a vulnerability affecting PaperCut NG and PaperCut MF.

We are aware of confirmed customer incidents and are treating this matter with the highest priority. Our investigation is ongoing. We will update this security bulletin as verified information becomes available, including indicators of compromise and remediation guidance.

Immediate action required

If your PaperCut NG/MF Application Server is accessible from the public internet, immediately restrict web access to trusted IP addresses only (e.g. internal IP addresses).

Use firewall rules, network access controls, or equivalent measures to ensure the PaperCut server’s web interfaces cannot be reached from untrusted internet addresses. Take this action now, even if you have not observed suspicious activity.

Emergency Patch Release

This is an emergency patch for customers with public-facing PaperCut NG/MF servers who are unable to take other mitigating action.

PaperCut MF

PaperCut NG

Note: If you use Card/ID number lookups from an external database, review the FAQ below before installing, this patch restricts the SQL queries that feature can use.

Who is potentially impacted

This advisory applies to all versions of:

• PaperCut NG
• PaperCut MF

Indicators of compromise and investigation guidance

The following may be indicators of compromise:

• Alerts from intrusion-detection, endpoint-security, or network-monitoring tools involving the PaperCut Application Server, particularly suspicious post-exploitation activity from pc-app.exe.

• Missing, unexpectedly truncated, or deleted PaperCut server.log files.

• Any of the following entries in server.log:
  ERROR No suitable driver found for jdbc:no:x

  ERROR DatabaseUtils - Database error looking up cardID: VALUES CAST

Important: The absence of the above indicators is not confirmation that a system has not been affected. PaperCut will publish validated, specific indicators and further guidance here as soon as they are available.

Current Status

FAQs

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