Which versions of Gitea act_runner are affected by EUVD-2026-39973?

Gitea act_runner (Docker backend, versions through 0.262.0) contains a critical container escape vulnerability (CVE-2026-58053, CVSS 9.4) for which publicly available exploit code exists.. A patch is available.

Is there a public PoC exploit available for EUVD-2026-39973?

Yes, a public proof-of-concept exploit is available for EUVD-2026-39973. Prioritise patching immediately. EPSS: 0.3%.

How to fix or mitigate EUVD-2026-39973?

Within 24 hours: Restrict workflow-execution permissions to a minimal trusted set of internal developers; disable Docker backend for act_runner if alternative backends exist, or take runners offline until mitigation is in place. Within 7 days: Audit all workflow execution history and identify any suspicious container operations or privilege escalations; map network access from runners to downstream systems to assess exposure. Within 30 days: Deploy mandatory runtime security controls (AppArmor/SELinux profiles with strict syscall allowlists); implement multi-approval workflow for any modifications to CI/CD configurations; evaluate migration to sandboxed runner alternatives.

Gitea act_runner EUVD-2026-39973

Q: What is the CVSS score of EUVD-2026-39973?

EUVD-2026-39973 has a CVSS 4.0 base score of 9.4 (Critical). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X. EPSS exploitation probability: 0.3%.

| CVE-2026-58053 CRITICAL

Improper Privilege Management (CWE-269)

2026-06-28 VulnCheck

GHSA-8qf9-pc52-j7cm

Privilege Escalation Gitea Docker Act Runner

9.4

CVSS 4.0 · Vendor: VulnCheck

Severity by source

Vendor (VulnCheck) PRIMARY

9.4 CRITICAL

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

vuln.today AI

9.9 CRITICAL

Attacker needs only authenticated workflow-run rights (PR:L) over the network with no user interaction; container-to-host escape changes scope (S:C) with full host C/I/A impact.

3.1 AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Primary rating from Vendor (VulnCheck).

CVSS VectorVendor: VulnCheck

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Lifecycle Timeline

Analysis Generated

Jun 28, 2026 - 02:30 vuln.today

CVSS changed

Jun 28, 2026 - 02:22 NVD

9.9 (CRITICAL) 9.4 (CRITICAL)

CVE Published

Jun 28, 2026 - 01:32 cve.org

CRITICAL 9.4

DescriptionCVE.org

Gitea act_runner with the Docker backend (through act 0.262.0) passes a workflow's container.options string to the Docker job container's HostConfig and, when configured with privileged: false, forces only the Privileged flag off while merging options such as --pid=host, --cap-add, and --security-opt unchanged. A user who can run a workflow on a Docker-backed runner can create a job container with host namespaces and broad capabilities and escape to the host as root despite privileged mode being disabled.

Articles & Coverage 1

News Critical Container Escape in Docker/Gitea act_runner - CVE-2026-58053 Jun 28, 2026

AnalysisAI

Container escape in Gitea act_runner (Docker backend, through act 0.262.0) lets an authenticated user with workflow-execution rights break out to the host as root even when privileged mode is disabled. The runner passes a workflow's container.options string straight into the Docker job container's HostConfig and only forces the Privileged flag off, leaving dangerous options like --pid=host, --cap-add, and --security-opt intact. Publicly available exploit code exists (reported by VulnCheck), though it is not listed in CISA KEV.

Technical ContextAI

Gitea act_runner is the CI/CD execution agent for Gitea (the act fork that interprets GitHub-Actions-style workflows). When using the Docker backend, each job runs in a container whose HostConfig is derived in part from the workflow author's container.options field. The flaw is a CWE-269 (Improper Privilege Management) hardening bypass: the runner's privileged: false setting is meant to be a security boundary, but the implementation only clears HostConfig.Privileged and merges the remaining attacker-supplied flags unchanged. Options such as --pid=host (shares the host PID namespace), --cap-add (grants Linux capabilities like CAP_SYS_ADMIN), and --security-opt (e.g. disabling seccomp/AppArmor) survive, so the container retains capabilities far beyond what disabling privileged mode implies - recreating the very isolation gaps privileged mode was supposed to remove.

RemediationAI

No vendor-released patched version of act_runner is identified in the provided data, so the exact fix version is not independently confirmed - consult the VulnCheck advisory (https://www.vulncheck.com/advisories/gitea-act-runner-container-hardening-bypass-via-workflow-container-options) for the latest fixed release and upgrade once available. As compensating controls: restrict workflow execution to trusted users only and never expose Docker-backed runners to untrusted or public-fork workflows (trade-off: limits open contribution/CI for external PRs); disable or strip the container.options capability so workflow authors cannot inject HostConfig flags (trade-off: breaks legitimate workflows that rely on custom options); enforce a Docker allow-list/deny-list or a runtime security policy that blocks --pid=host, --cap-add, and --security-opt regardless of workflow input; and where feasible run runners with rootless Docker or in disposable, isolated VMs so a successful escape lands in a throwaway host (trade-off: added operational overhead).