# CVE-2026-77156: ast-cli: Path traversal in tar extraction on Linux/macOS allows writes outside the install directory


- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 22 Oct 2026
- **Updated:** 22 Oct 2026
- **Also known as:** GHSA-9gff-3q53-q75x

## What is CVE-2026-77156?

CVE-2026-77156 is a medium-severity vulnerability in github.com/checkmarx/ast-cli, published on 22 Oct 2026. 

### Official description

Incomplete validation of extracted archive entry paths in ast-cli's tar extraction logic on Linux and macOS (used when installing the Vorpal ASCA real-time engine and the SCA Resolver) would allow a malicious tar archive containing absolute or traversal path entries to write files outside the install directory. Windows builds were not affected, as the Windows extractor performs this path validation.

Exploitation required substituting the archive served at "download.checkmarx.com". An attacker able to compromise that server and replace the archive could write arbitrary, executable files to arbitrary filesystem paths via this path traversal.

Extraction now validates that each entry's destination path resolves within the working directory and rejects absolute paths.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-77156?


## How do I fix CVE-2026-77156?

No fix has been published for CVE-2026-77156 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-77156 being exploited?

There is no known exploitation of CVE-2026-77156 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-77156 and fix it if it is affected.

What it is: CVE-2026-77156 is a medium-severity vulnerability in github.com/checkmarx/ast-cli, published on 22 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-77156 in the wild and no public exploit code.

Affected product: github.com/checkmarx/ast-cli. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-77156/ (Markdown: https://insights.sbomify.com/CVE-2026-77156/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-77156
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-77156
- OSV: https://osv.dev/vulnerability/CVE-2026-77156

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-77156/
Summaries are generated and may contain mistakes; the official description above is the record.