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Container Hardening Bypass in Gitea act_runner Docker Backend

IdentifiersCVE-2026-58053CWE-693

CVE-2026-58053 is a critical container hardening bypass affecting Gitea act_runner when using the Docker backend through act 0.262.0. The flaw arises because a workflow's container.options string is merged into the Docker job container HostConfig. When the runner is configured with privileged: false, it only forces the Docker Privileged flag to false, but does not sanitize or strip other dangerous Docker options. As a result, workflow-supplied flags such as --pid=host, --cap-add, and --security-opt are preserved and applied to the job container. An attacker with the ability to run a workflow on a Docker-backed runner can abuse these options to create a container with host namespaces and expanded capabilities, enabling escape from the containerized job environment to the underlying host as root despite privileged mode being disabled.

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ANALYST BRIEF

Impact, mitigation & remediation

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Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation can result in full host compromise from a workflow execution context. An attacker can bypass intended runner isolation, obtain root-level access on the runner host, and potentially access or modify host resources, secrets, other workloads, and runner infrastructure. The impact includes high confidentiality, integrity, and availability consequences because the attacker can escape the job container and operate on the host with elevated privileges.

Mitigation

If you can’t patch tonight, do this now.

Until patched versions are deployed, do not run untrusted workflows on Docker-backed runners. Review and restrict which Docker container options may be specified in workflows, and explicitly disallow dangerous flags such as --pid=host, capability additions via --cap-add, and unsafe --security-opt values. Where possible, use more strongly isolated runner backends or additional host/container confinement controls to reduce the risk of container escape.

Remediation

Patch, then assume compromise.

Update Gitea act_runner and the underlying runner components to a version that addresses this issue and properly sanitizes workflow-supplied Docker job container options. Ensure runner configuration does not rely solely on privileged: false as a security boundary, and deploy a fixed version that rejects or strips unsafe HostConfig-related options originating from workflow container.options.
PUBLIC EXPLOITS

Exploits

No public exploits tracked yet. Mallory keeps watching.

VALID 0 / 0 TOTALView more in app

No public exploit code observed for this vulnerability.

ACTIVITY FEED

Recent activity

8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.

8 SOURCESView more in app
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Threat actor evidence

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Detection signatures

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Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity7

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES
MITRE CVE
cve.org · CVE-2026-58053
NVD
nvd.nist.gov/vuln/detail/CVE-2026-58053
MITRE CWE · CWE-693
cwe.mitre.org