critical CVSS 10

CVE-2026-53576·Docker vulnerability

Kestra 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.

Severity
critical
Software
Docker
Fixed in
1.3.21
Published
2026-06-26

Affected versions

From: 1.1.0

Until: 1.3.21

Fixed in: 1.3.21

How to fix this CVE

Update Docker to version 1.3.21 or later to patch an authentication bypass vulnerability in the REST API that allows unauthenticated remote code execution. The flaw permits attackers to bypass credential checks by manipulating request paths, creating malicious workflows that execute arbitrary commands with root privileges inside containers. Immediate patching is critical, especially for deployments with Docker socket mounting enabled.

sudo dnf upgrade docker-ce

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST|GET /api/v1/[^/]+/(flows|executions)[^/]*/?configs HTTP/1\.1.*Authorization: |GET /api/v1/[^/]+/(flows|executions).*(configs|namespace).*unauthenticated.*

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 require authentication for all requests to /api/v1/*/flows, /api/v1/*/executions, and /api/v1/*/namespaces endpoints. Implement a WAF rule that rejects any API requests to these paths lacking a valid Authorization header (Bearer token or Basic Auth). Additionally, enforce strict path validation to reject requests with suspicious path segments like 'configs' appended to privileged endpoints.

How to check if you are affected

  1. Step 1: Check the installed Docker version with `docker --version` and compare against version 1.3.21
  2. Step 2: Verify if the REST API endpoint /api/v1/{tenant}/flows or /api/v1/{tenant}/executions is accessible without authentication by attempting unauthenticated curl requests to these paths
  3. Step 3: Search application logs and Docker daemon logs for suspicious unauthenticated API requests containing 'configs' in the path or requests to flow creation and execution endpoints from unknown IPs
  4. Step 4: Confirm the patch by checking `docker --version` returns 1.3.21 or higher and attempt the same unauthenticated API requests—they should now fail with authentication errors

Indicators of compromise

  • HTTP POST requests to /api/v1/*/flows/configs without Authorization header
  • HTTP POST requests to /api/v1/*/executions/*/configs without Authorization header
  • Shell or Process task definitions in flow creation payloads from unauthenticated sources
  • Successful container command execution logs originating from unauthenticated REST API calls

FAQ

What is CVE-2026-53576?

This is an authentication bypass vulnerability in Kestra's REST API where malformed requests ending in '/configs' circumvent credential validation, allowing unauthenticated attackers to create and execute workflows that run arbitrary code as root inside containers.

Is CVE-2026-53576 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog, and no public exploit code is available. However, the critical CVSS 10.0 score indicates immediate patching is warranted.

What versions of Docker are affected by CVE-2026-53576?

Kestra versions 1.1.0 through 1.3.20 are vulnerable. The vulnerability is patched in version 1.3.21 and later.

How do I check if my server is vulnerable to CVE-2026-53576?

Run `docker --version` to confirm your installed version. If it is below 1.3.21, your deployment is vulnerable. Additionally, test unauthenticated access to the API endpoint: `curl -i http://localhost:8080/api/v1/tenant/flows/configs` should return an authentication error if properly patched.

Does Defensia detect CVE-2026-53576?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker is installed on a monitored server, CVE-2026-53576 will appear in your dashboard with remediation steps.

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References

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