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CVE-2026-63395VulnerabilityPublished

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

Affects isomorphic-gitSource GCVE Database

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Authoritative record:CVE-2026-63395· High 8.8

Not known to be exploited · CVSS 8.8 High : upgrade to 1.38.6 soon.

Data as of 9 Nov 2026, 23:24 UTC

CVSS 3.1 base score
8.8High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (GitHub_M)CVSS 3.18.8
EPSS
0.7% chance of exploitation in 30 days – higher than 54% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 1.38.6
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

What to do

Upgrade isomorphic-git to 1.38.6.

Affected software

ProductAffectedFixed in
npmisomorphic-gitAffected
  • <1.38.6
Fixed in
  • 1.38.6

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in isomorphic-git version 1.38.6. Users should upgrade to this version or later to prevent exploitation. The fix implements checks to refuse traversal of symlinks in leading path components during checkout, mirroring canonical Git behavior. No additional mitigation is required once patched.

Description

isomorphic-git versions prior to 1.38.6 contain a vulnerability in the checkout process where directory symlinks are not properly checked before writing files. This allows a malicious repository to write files outside the intended working directory by exploiting directory symlinks, potentially leading to arbitrary file writes on the host system. The impact varies by filesystem provider, with the highest risk on POSIX systems using Node's fs module, where remote code execution (RCE) is possible by injecting attacker-controlled files such as SSH authorized keys or Git hooks. The issue is fixed in version 1.38.6.

References

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