high CVSS 8.2

CVE-2026-40893·Docker vulnerability

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, Gotenberg only checks if the tag is exactly FileName, so System:FileName slips right through and ExifTool happily renames the file. This allows remote attackers to move, rename, and change permissions for arbitrary files. This vulnerability is fixed in 8.31.0.

Severity
high
Software
Docker
Fixed in
8.31.0
Published
2026-05-14

Affected versions

Until: 8.31.0

Fixed in: 8.31.0

How to fix this CVE

Update Docker and Gotenberg to version 8.31.0 or later to patch a critical file manipulation vulnerability in the ExifTool integration. This vulnerability allows remote attackers to rename, move, and alter permissions of arbitrary files through improper tag validation in Gotenberg's PDF processing pipeline. Immediate patching is recommended to prevent unauthorized file system operations.

sudo dnf update docker-ce

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST requests to Gotenberg PDF conversion endpoints with ExifTool tag parameters containing 'System:FileName', 'System:FileModifyDate', or other namespaced tag variations that bypass simple string matching validation

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement request filtering to block POST/GET parameters containing ExifTool tag patterns matching regex: /(System|Exif|Iptc|Xmp):[A-Za-z]+/ in Gotenberg API endpoints; additionally whitelist only expected PDF processing parameters and reject requests with unexpected metadata fields

How to check if you are affected

  1. Check installed Docker version: docker --version and verify Gotenberg version within the container with docker exec <container_id> gotenberg --version
  2. Confirm Gotenberg is exposed to untrusted networks: docker ps -a and inspect network bindings with docker inspect <container_id> | grep -i ports
  3. Search container logs for ExifTool tag processing: docker logs <container_id> | grep -i 'exiftool\|tag\|filename' to identify suspicious tag patterns
  4. Verify the patch: docker exec <container_id> gotenberg --version should return 8.31.0 or higher

FAQ

What is CVE-2026-40893?

CVE-2026-40893 is a file manipulation vulnerability in Gotenberg's PDF processing API where insufficient tag validation allows attackers to bypass security checks using crafted ExifTool tags (e.g., System:FileName instead of FileName), enabling unauthorized file operations.

Is CVE-2026-40893 being actively exploited?

No, CVE-2026-40893 is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available, though the vulnerability should be patched proactively given its high severity.

What versions of Docker are affected by CVE-2026-40893?

All versions of Gotenberg prior to 8.31.0 are affected when running within Docker environments. The vulnerability exists in the Gotenberg application itself, not Docker directly.

How do I check if my server is vulnerable to CVE-2026-40893?

Run docker exec <container_id> gotenberg --version and compare the output to 8.31.0. If the version is lower, the system is vulnerable. Also verify that Gotenberg containers are accessible from untrusted networks.

Does Defensia detect CVE-2026-40893?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker with Gotenberg is installed on a monitored server, CVE-2026-40893 will appear in your dashboard with remediation steps.

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References

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