# CVE-2026-63395: isomorphic-git symlink path traversal in checkout

Source: https://junglewise.ai/threats/cve-2026-63395-isomorphic-git-is-a-pure-javascript-implementation-of-git-for  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-03. Updated: 2026-11-03  
License: CC BY 4.0 with a link back

CVE-2026-63395 · Severity: high · CVSS 8.8 · Published 2026-11-03

isomorphic-git is a JavaScript Git implementation used in Node.js and browser environments. A flaw in its git.checkout function allows writing files outside the intended working directory by following symbolic links placed in parent directory paths. An attacker controlling a malicious repository can achieve arbitrary file writes on the host system, potentially leading to code execution on Linux and macOS systems, while Windows and browser environments have limited exposure.

Technologies: [Isomorphic-Git](https://junglewise.ai/threats/technologies/isomorphic-git-isomorphic-git), [isomorphic-git (npm)](https://junglewise.ai/threats/technologies/isomorphic-git). Vendors: [Isomorphic-Git](https://junglewise.ai/threats/vendors/isomorphic-git), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-63395 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63395 being exploited in the wild.

**How severe is CVE-2026-63395?** High severity, with a CVSS score of 8.8, published 3 November 2026.

**Which products and versions are affected?** Isomorphic-Git prior to 1.38.6; isomorphic-git (npm) <= 1.38.5, SEMVER:introduced=0,fixed=1.38.6.

**Is there a fix for CVE-2026-63395?** Yes. isomorphic-git (npm): upgrade to 1.38.6 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-63395 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-63395?** Check whether you run Isomorphic-Git or isomorphic-git (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- isomorphic-git (npm): upgrade to 1.38.6 or later

  ```sh
  npm install isomorphic-git@1.38.6
  ```


## Technical details

The vulnerability is a path traversal flaw in the git.checkout operation where symlinked leading directory components are not validated before writing child paths. An attacker can first insert a directory symlink into the repository and later replace it with a tree containing a child file, triggering the vulnerability during clone or pull operations. On Node.js with Linux/macOS file systems, the OS resolves symlinks during writes, allowing files to be written outside the working tree; Windows typically blocks this without elevated privileges, and browser/in-memory providers are limited to their virtual filesystem.

## Affected products

- isomorphic-git isomorphic-git prior to 1.38.6

## Identifiers

- CVE-2026-63395
- GHSA-9qw7-j9xw-fv9c

## Timeline

- 2026-11-03: disclosed
- 2026-07-01: patched

## References

- [https://github.com/isomorphic-git/isomorphic-git/commit/823843d1cd19182df79bc907c767f5bcecb39a0b](https://github.com/isomorphic-git/isomorphic-git/commit/823843d1cd19182df79bc907c767f5bcecb39a0b)
- [https://github.com/isomorphic-git/isomorphic-git/pull/2370](https://github.com/isomorphic-git/isomorphic-git/pull/2370)

## Related threats

- [isomorphic-git path traversal in tree parser](https://junglewise.ai/threats/cve-2026-63478-isomorphic-git-is-a-pure-javascript-implementation-of-git-for)
- [isomorphic-git unbound buffer allocation in packfile delta](https://junglewise.ai/threats/cve-2026-63476-isomorphic-git-is-a-pure-javascript-implementation-of-git-for)
- [isomorphic-git circular symref denial of service](https://junglewise.ai/threats/cve-2026-63475-isomorphic-git-is-a-pure-javascript-implementation-of-git-for)
- [isomorphic-git directory traversal via malicious file paths](https://junglewise.ai/threats/cve-2021-30483-isomorphic-git-directory-traversal-via-malicious-file-paths)