high · CVSS 8.8

CVE-2026-63395

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

Published 3 Nov 2026 · Source updated 3 Nov 2026 · Retrieved 2026-11-05 18:01 UTC

Statance checks for CVE-2026-63395. Connected servers are checked automatically against the fixed versions their distribution or package ecosystem has published for it, including app dependency lockfiles. Check my servers ↗

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What happened?

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.

Description supplied by CVE Program. Formatting is simplified; follow the original advisory for full details.

Affected software and versions

Source-provided software and version information
Software	Version information	Fixed version
isomorphic-gitisomorphic-git	affected: < 1.38.6	See vendor advisory

Version information comes from the source record and can include unaffected products and exceptions. Distribution packages may contain backported fixes: an older upstream version alone does not prove a server is affected.

Is it being exploited?

This CVE was not listed in the CISA catalogue at our last retrieval. This does not establish that exploitation is absent.

CISA data retrieved 2026-11-06 16:38 UTC. Check CISA ↗

How to respond

Confirm the product, installed package version, and any configuration requirements in the vendor advisory.
Follow the vendor’s remediation or workaround guidance in the references below. Structured fixed-version data is unavailable here; the publisher’s description may include a fix or workaround.
Restart affected services if required, then verify the running version. Known exploitation may warrant investigation as well as patching.

Sources and remediation references

This public advisory does not determine whether a particular server is affected. Records are refreshed as sources change; verify urgent decisions against the original advisory.

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