CVE-2026-63395

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

Published Nov 3, 2026 CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed
Description
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 solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-9qw7-j9xw-fv9c isomorphic-git: Arbitrary file write outside of working tree via directory symlink during checkout (potential RCE)
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Isomorphic-git
Isomorphic-git isomorphic-git
Vendors & Products Isomorphic-git
Isomorphic-git isomorphic-git
Type Values Removed Values Added
Description 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.
Title isomorphic-git: Arbitrary file write outside the working tree via a directory symlink during checkout (potential RCE)
Weaknesses CWE-22
CWE-59
References
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Nov 3, 2026, 9:30 PM
Reserved
Jul 16, 2026, 5:39 PM
Status
Deferred
Published
Nov 3, 2026, 8:18 PM
Modified
Nov 3, 2026, 10:19 PM
Severity
Important
Public date
Nov 3, 2026, 7:48 PM