compose-lint: Compose file text can issue GitHub Actions workflow commands through the compose-lint Action

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

5.3 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/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 · score source

EPSS

• CVE-2026-123369: 0.38% estimated exploitation activity in the next 30 days; percentile 32.35 (FIRST EPSS, 2026-11-10). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The GitHub Actions runner treats certain text in a step's output as commands. The legacy form, `##[command]`, is recognized anywhere in a line. compose-lint's text report prints service names, environment keys and lines of the Compose file, and it does not neutralize `##[`. Inside the compose-lint Action, a Compose file from a pull request can therefore: - create fake error or warning annotations on the pull request (`##[error]`, `##[warning]`) - fold the rest of the log, including the real verdict, out of sight (`##[group]`) - blank out chosen strings for the rest of the log (`##[add-mask]`) GitHub has postponed removing the deprecated `set-output` log command, so the runner still honors it. A test run of the Action on a GitHub-hosted runner confirmed that a `::set-output` line from a Compose file is processed. Whether it can override the Action's own `sarif-written` output, which decides whether the SARIF upload step runs, has not been tested. The exit code and the…

Published by the source

10 Nov 2026, 15:56 UTC

Last modified by the source

11 Nov 2026, 02:57 UTC

Source last checked

11 Nov 2026, 07:05 UTC

1. Revision 2 · amended · 11 Nov 2026

   Amended from osv record GHSA-6f4g-xm8v-pgv6

2. Revision 1 · created · 10 Nov 2026

   Published from ghsa record GHSA-6f4g-xm8v-pgv6

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# Patch Next advisory brief: CVE-2026-123369

Advisory: compose-lint: Compose file text can issue GitHub Actions workflow commands through the compose-lint Action
IDs: CVE-2026-123369, GHSA-6f4g-xm8v-pgv6
Record: https://patchnext.com/advisories/cve-2026-123369 (revision 2, source checked 11 Nov 2026, 07:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: compose-lint 0.31.0; tmatens/compose-lint 0.31.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI compose-lint: affected < 0.31.0; fixed in 0.31.0
- GitHub Actions tmatens/compose-lint: affected >= 0.2.0, < 0.31.0; fixed in 0.31.0

## Suggested inspection (read-only)
- `python -m pip show compose-lint`: prints the installed version. Run with the environment that serves production active.
- GitHub Actions tmatens/compose-lint: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on compose-lint, tmatens/compose-lint.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-6f4g-xm8v-pgv6 (GitHub-reviewed advisory GHSA-6f4g-xm8v-pgv6 lists affected ranges: GitHub Actions tmatens/compose-lint >=0.2.0 =0 <=0.30.0)
- Verified: https://osv.dev/vulnerability/GHSA-6f4g-xm8v-pgv6 (OSV record GHSA-6f4g-xm8v-pgv6 lists affected ranges: GitHub Actions tmatens/compose-lint >=0.2.0 =0 <0.31.0 (fixed))

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