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.

Related Docker CVEs

CVE-2026-40281CVSS 10Gotenberg is a Docker-powered stateless API for PDF files. In versions 8.30.1 and earlier, the metadata write endpoint validates metadata keys for control characters but leaves metadata values unsanitized. A newline character in a metadata value splits the ExifTool stdin line into two separate arguments, allowing injection of arbitrary ExifTool pseudo-tags such as -FileName, -Directory, -SymLink, and -HardLink. This is a bypass of the incomplete key-sanitization fix introduced in v8.30.1. An unauthenticated attacker can rename or move any PDF being processed to an arbitrary path in the container filesystem, overwrite arbitrary files, or create symlinks and hard links at arbitrary paths.
CVE-2026-53576CVSS 10Kestra is an open-source, event-driven orchestration platform. Prior to 1.0.45 and 1.3.21, the authentication filter for the REST API (@Filter("/api/v1/**")) treats any request whose path ends in /configs as the public instance-config endpoint and forwards it without a credential check. kestra addresses its resources by URL path segments that the caller chooses (/api/v1/{tenant}/flows/{namespace}, /api/v1/{tenant}/executions/{namespace}/{id}, /api/v1/{tenant}/namespaces/{namespace}/kv/{key}). An anonymous caller picks the literal configs as the final segment, and the request bypasses Basic-Auth entirely. Because the bypass reaches the flow-create and execution-trigger routes, an unauthenticated caller creates a flow containing a Shell or Process task and runs it. The task executes as root inside the kestra container. The official docker-compose.yml mounts /var/run/docker.sock, so root in the container reaches the host Docker daemon. This vulnerability is fixed in 1.0.45 and 1.3.21.
CVE-2026-26216CVSS 10Crawl4AI versions prior to 0.8.0 contain a remote code execution vulnerability in the Docker API deployment. The /crawl endpoint accepts a hooks parameter containing Python code that is executed using exec(). The __import__ builtin was included in the allowed builtins, allowing unauthenticated remote attackers to import arbitrary modules and execute system commands. Successful exploitation allows full server compromise, including arbitrary command execution, file read and write access, sensitive data exfiltration, and lateral movement within internal networks.
CVE-2026-44329CVSS 10free5GC is an open-source implementation of the 5G core network. Prior to 4.2.2, free5GC's SMF mounts the UPI management route group without OAuth2/bearer-token authorization middleware. A network attacker who can reach SMF on the SBI can hit UPI endpoints with no Authorization header at all, and the requests reach the SMF business handlers. In the running Docker lab this was directly demonstrated for read (GET /upi/v1/upNodesLinks), write (POST /upi/v1/upNodesLinks with attacker-controlled UP-node and link payload), and delete (DELETE /upi/v1/upNodesLinks/{nodeID}) operations. This vulnerability is fixed in 4.2.2.
CVE-2026-33587CVSS 10Lack of user input sanitisation in Open Notebook v1.8.3 allows the application user to execute Python code (and subsequently OS commands) on the docker container via Server-Side Template Injection (SSTI) for user-created transformations.

References

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