high CVSS 7.5

CVE-2026-42594·Docker vulnerability

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.32.0, the webhook middleware spawns a goroutine that holds a reference to the request's echo.Context after the synchronous handler returns ErrAsyncProcess and Echo recycles the context back to its sync.Pool. When a concurrent request claims the recycled context, c.Reset() clears the store. If the webhook goroutine reaches hardTimeoutMiddleware at that moment, an unchecked type assertion on a nil store entry panics outside any recover() scope, crashing the Gotenberg process. Any anonymous caller reaches the webhook path (default webhook-deny-list filters only the webhook destination, not the submitter). A single-source stress of ~24 webhook requests plus ~60 GET /version requests crashes the process in about two seconds. This vulnerability is fixed in 8.32.0.

Severity
high
Software
Docker
Fixed in
8.32.0
Published
2026-05-14

Affected versions

Until: 8.32.0

Fixed in: 8.32.0

How to fix this CVE

Update Docker to version 8.32.0 or later to fix a denial-of-service vulnerability in Gotenberg's webhook middleware that can crash the container process. The vulnerability stems from improper context lifecycle management when handling concurrent webhook requests, allowing unauthenticated attackers to trigger a panic that terminates the service. Patch immediately in production environments where Gotenberg is deployed.

sudo dnf update docker-ce

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /webhook HTTP/1.1.*\r\nContent-Length: [0-9]+.*panic|goroutine|hardTimeoutMiddleware|nil pointer|recovered

WAF mitigation (if patching is not yet possible)

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

Block or rate-limit POST requests to /webhook endpoints if Gotenberg is exposed. Implement IP whitelisting for webhook submissions and require authentication headers to restrict access to known callers only.

How to check if you are affected

  1. Run 'docker --version' to check your Docker version; versions prior to 8.32.0 are vulnerable
  2. Inspect running containers with 'docker ps' and check if Gotenberg is deployed; confirm the image tag corresponds to a version before 8.32.0
  3. Review container logs with 'docker logs <container-id>' for panic messages or runtime errors containing 'hardTimeoutMiddleware' or nil pointer dereferences
  4. After patching, re-run 'docker --version' and restart affected containers to confirm the updated version is loaded

FAQ

What is CVE-2026-42594?

This vulnerability affects Gotenberg's webhook middleware, which improperly manages Echo framework contexts in concurrent goroutines. When a recycled context is reset while a webhook handler is still executing, an unchecked type assertion on a nil value triggers a panic outside recovery scope, crashing the entire Gotenberg process without authentication required.

Is CVE-2026-42594 being actively exploited?

No, this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, it is trivial to trigger and can be weaponized with minimal effort.

What versions of Docker are affected by CVE-2026-42594?

Gotenberg versions prior to 8.32.0 are vulnerable. When Gotenberg runs in a Docker container, the affected version of Gotenberg—not Docker itself—is the vulnerable component, though Docker is the distribution mechanism.

How do I check if my server is vulnerable to CVE-2026-42594?

Run 'docker images | grep gotenberg' to list Gotenberg images, then inspect each image's tag against version 8.32.0. Alternatively, execute 'docker inspect <image-id>' and check the image creation details or run the container and query its API version endpoint.

Does Defensia detect CVE-2026-42594?

Yes — Defensia's CVE advisory scanner compares installed Docker and container image versions against the NVD database. If Gotenberg or Docker is detected on a monitored server, CVE-2026-42594 will appear in your dashboard with remediation steps.

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References

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