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Fencer Intel
high 8.8

CVE-2026-63395 json

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

published 6d ago modified 5h ago also EUVD-2026-116274 , GHSA-9qw7-j9xw-fv9c

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 54%
public exploits
0
none known

Summary

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.

Patch / fix

  • npm isomorphic-git 1.38.6

Is CVE-2026-63395 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-63395 updated cvss 8.8

isomorphic-git: isomorphic-git: Arbitrary code execution via directory symlink traversal

  • Red Hat OpenShift Serverless openshift-serverless-1/logic-rhel9-operator Red Hat Developer Hub 1 rhdh/rhdh-hub-rhel9, rhdh/red-hat-developer-hub-backstage-plugin-orchestrator-backend, rhdh/red-hat-developer-hub-backstage-plugin-scaffolder-backend-module-orchestrator Red Hat Self-service automation portal 2 ansible-automation-platform/automation-portal, ansible-automation-platform/bootc-automation-portal-rhel9
    affected: workaround, no fix available

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
6d ago

Exploit prediction

0.72% chance of exploitation in the next 30 days, higher than 54% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • github.com https://github.com/isomorphic-git/isomorphic-git/security/advisories/GHSA-9qw7-j9xw-fv9c referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
GitHub 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm isomorphic-git
<1.38.6
1.38.6

Affected products

  • isomorphic-git isomorphic-git

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory
  • CWE-59 Improper Link Resolution Before File Access

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.