# CVE-2026-63395: isomorphic-git: Arbitrary file write outside the working tree via a directory symlink during checkout (potential RCE)

Status: published. Published: 2026-11-03. Updated: 2026-11-03.

isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git's git.checkout writes new child paths through symlinked leading directory components without checking them. A malicious repository can first place a directory symlink and later replace the tree state with a child file beneath that path; the usual trigger is a clone followed by a later pull, while a single clone can trigger the issue when a symlink already exists or the consuming application accesses the tree. With Node fs on Linux or macOS, the operating system can resolve the write outside the working tree, permitting arbitrary host file writes and possible code execution. Node fs on Windows usually blocks the symlink plant without additional privilege, and browser or in-memory providers limit impact to their virtual filesystem and are affected only when they implement symlink creation and following. This issue is fixed in version 1.38.6.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- isomorphic-git / isomorphic-git: < 1.38.6 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 8.8 (high); CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-22, CWE-59

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/isomorphic-git/isomorphic-git/security/advisories/GHSA-9qw7-j9xw-fv9c (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/isomorphic-git/isomorphic-git/pull/2370 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/isomorphic-git/isomorphic-git/commit/823843d1cd19182df79bc907c767f5bcecb39a0b (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/isomorphic-git/isomorphic-git/releases/tag/v1.38.6 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-63395; retrieved 2026-11-03; source updated 2026-11-03

Revision: 19a5a62592fae0d03a1cfe6841dd92ab96939bd82069ad5e62a70367c89c09e5

Canonical: https://y2.dev/cve/CVE-2026-63395

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