Bug 2566192 (CVE-2026-63395)

Summary: CVE-2026-63395 isomorphic-git: isomorphic-git: Arbitrary code execution via directory symlink traversal
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: abarbaro, alizardo, dhanak, drosa, dschmidt, dsimansk, ikhan, jchui, jhe, jlanda, kingland, kshier, ktsao, mnovotny, nboldt, oaljalju, psrna, rbobbitt, sausingh, simaishi, stcannon, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in isomorphic-git. This vulnerability allows a remote attacker to achieve arbitrary code execution by tricking a user or automated process into checking out a specially crafted repository. During the checkout operation, the library writes files through directory symbolic links without proper validation, enabling arbitrary files to be written outside the intended working directory on the host system.
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Description OSIDB Bzimport 2026-11-03 20:03:29 UTC 
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.