compose-lint: .env read through a symlink outside the project can expose the CI job's environment

Exploitation

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

CVSS 4.0

2.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/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-2026-123368: 0.48% estimated exploitation activity in the next 30 days; percentile 41.53 (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 compose-lint fills in `${VAR}` references from the `.env` file next to the Compose file. It is meant to read nothing outside the project directory, and `env_file:`, `include:` and `extends:` paths are checked for that. The `.env` read is not. If `.env` is a symlink, compose-lint follows it wherever it points. A pull request can add a `.env` symlink to any file on the CI runner and a Compose file that references a variable from it. compose-lint substitutes the value and quotes it in finding messages, which go to the log and to JSON and SARIF output. The worst target is `/proc/self/environ`, the linter's own environment. The Compose file only needs to reference the name of the first variable in it: because that file separates variables with NUL bytes rather than newlines, the substituted value is the entire rest of the environment. On a CI runner that environment holds whatever the workflow put there, including secrets. GitHub masks registered secrets in the job log, but not…

Published by the source

10 Nov 2026, 15:56 UTC

Last modified by the source

10 Nov 2026, 16:15 UTC

Source last checked

11 Nov 2026, 07:05 UTC

1. Revision 2 · amended · 11 Nov 2026

   Amended from osv record GHSA-6wcv-rj3c-mhv3

2. Revision 1 · created · 10 Nov 2026

   Published from ghsa record GHSA-6wcv-rj3c-mhv3

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-123368

Advisory: compose-lint: .env read through a symlink outside the project can expose the CI job's environment
IDs: CVE-2026-123368, GHSA-6wcv-rj3c-mhv3
Record: https://patchnext.com/advisories/cve-2026-123368 (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: Low (CVSS 2.3)
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 >= 0.22.0, < 0.31.0; fixed in 0.31.0
- GitHub Actions tmatens/compose-lint: affected >= 0.22.0, < 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-6wcv-rj3c-mhv3 (GitHub-reviewed advisory GHSA-6wcv-rj3c-mhv3 lists affected ranges: PyPI compose-lint >=0.22.0 =0.22.0 <=0.30.0)
- Verified: https://osv.dev/vulnerability/GHSA-6wcv-rj3c-mhv3 (OSV record GHSA-6wcv-rj3c-mhv3 lists affected ranges: PyPI compose-lint >=0.22.0 =0.22.0 <0.31.0 (fixed))

Commands are suggestions: review each one before running it.