# CVE-2026-123370: compose-lint: `fix --apply` can delete a line the user did not select, including a security setting


- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 9 Nov 2026
- **Updated:** 9 Nov 2026
- **Also known as:** GHSA-65v8-q222-64xx

## What is CVE-2026-123370?

CVE-2026-123370 is a medium-severity vulnerability in tmatens compose-lint, published on 9 Nov 2026. 

### Official description

compose-lint is a Docker Compose security linter that identifies dangerous misconfigurations before deployment. From 0.9.0 until 0.18.0, compose-lint's YAML parser recognizes lone carriage returns and Unicode line separators U+0085, U+2028, and U+2029 as line breaks while fix position conversion counts only newline characters. A pull request can place one of these separators in a quoted value so fix --apply shifts each later edit and deletes the line after the selected target, including an unselected network or other security setting. The resulting Compose file can remain valid, post-edit checks can pass, and the command can report a successful fix even though the dry-run diff was the only place showing the extra deletion. This issue is fixed in version 0.18.0.

Weakness: CWE-193 (Off-by-one Error)

## Which versions are affected by CVE-2026-123370?

1 open source package ship an affected version, including compose-lint.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `compose-lint` | PyPI | From 0.9.0 | 0.18.0 |

## How do I fix CVE-2026-123370?

Upgrade compose-lint to 0.18.0 or later.

## Is CVE-2026-123370 being exploited?

There is no known exploitation of CVE-2026-123370 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-123370 and fix it if it is affected.

What it is: CVE-2026-123370 is a medium-severity vulnerability in tmatens compose-lint, published on 9 Nov 2026. 
Exploitation: There is no known exploitation of CVE-2026-123370 in the wild and no public exploit code.

Affected packages and fixed versions:
- compose-lint (PyPI): affected from 0.9.0; fixed in 0.18.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-123370/ (Markdown: https://insights.sbomify.com/CVE-2026-123370/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-123370
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-123370
- OSV: https://osv.dev/vulnerability/CVE-2026-123370

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-123370/
Summaries are generated and may contain mistakes; the official description above is the record.