# CVE-2026-63475: isomorphic-git circular symref denial of service

Source: https://junglewise.ai/threats/cve-2026-63475-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-2026-63475 · Severity: medium · CVSS 4.3 · Published 2026-11-03

isomorphic-git is a JavaScript Git implementation used in Node.js and browser applications. After cloning from a malicious Git repository, circular symbolic references can be persisted on disk, causing Git operations to hang indefinitely without terminating. This leaves the repository permanently unusable and causes a persistent denial of service.

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-2026-63475 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-63475 being exploited in the wild.

**How severe is CVE-2026-63475?** Medium severity, with a CVSS score of 4.3, published 3 November 2026.

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

**Is there a fix for CVE-2026-63475?** 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-2026-63475 attacked?** It is attacked over the network or from the adjacent network, in a software library.

**Am I affected by CVE-2026-63475?** 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 exists in GitRefManager.resolve() which follows symbolic references without cycle detection or a depth limit. A remote server can supply circular symref= capabilities through updateRemoteRefs that are persisted locally. An attacker performing a man-in-the-middle attack or hosting a malicious repository can trigger this condition; the affected operations (log, status, checkout, branch) do not require authentication or user interaction beyond the initial clone.

## Affected products

- isomorphic-git isomorphic-git before 1.38.6

## Identifiers

- CVE-2026-63475
- GHSA-96wc-2m84-2cj7

## 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 symlink path traversal in checkout](https://junglewise.ai/threats/cve-2026-63395-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)