Gotenberg has an ExifTool Dangerous Tag Blocklist Bypass via Group-Prefixed Tag Names that Allows Arbitrary File Rename and Move

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.2 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

EPSS

• CVE-2026-40893: 0.35% estimated exploitation activity in the next 30 days; percentile 28.34 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Gotenberg blocks certain ExifTool tag names like FileName and Directory to stop attackers from renaming or moving files on the server. But ExifTool allows a longer form of the same tag — System:FileName — which does the exact same thing. Gotenberg only checks if the tag is exactly FileName, so System:FileName slips right through and ExifTool happily renames the file. No login is needed. One HTTP request is enough. This bypasses the fix from GHSA-qmwh-9m9c-h36m. Details Think of it like a nightclub bouncer with a blocklist of banned names. The blocklist says "Block anyone named John." A person shows up and says "I'm Mr. John." The bouncer checks — "Mr. John" is not "John" — so he lets them in. But inside the club, everyone knows Mr. John IS John. That's exactly what happens here: The blocklist (exiftool.go line 275-280) blocks these tag names: The check (exiftool.go line 295-301) compares what the user sent against this list: System:FileName is not equal to FileName (one is 16…

Published by the source

4 May 2026, 19:21 UTC

Last modified by the source

14 May 2026, 20:51 UTC

Source last checked

26 Oct 2026, 15:22 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-62p3-hvxx-fxg4

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# Patch Next advisory brief: CVE-2026-40893

Advisory: Gotenberg has an ExifTool Dangerous Tag Blocklist Bypass via Group-Prefixed Tag Names that Allows Arbitrary File Rename and Move
IDs: CVE-2026-40893, GHSA-62p3-hvxx-fxg4
Record: https://patchnext.com/advisories/cve-2026-40893 (revision 1, source checked 26 Oct 2026, 15:22 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/gotenberg/gotenberg/v8: affected <= 8.30.1

## Suggested inspection (read-only)
- Go github.com/gotenberg/gotenberg/v8: check the installed version with your package manager.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/gotenberg/gotenberg/v8.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-62p3-hvxx-fxg4 (GitHub-reviewed advisory GHSA-62p3-hvxx-fxg4 lists affected ranges: Go github.com/gotenberg/gotenberg/v8 >=0 <=8.30.1)

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