Description
isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers. Prior to 1.38.6, isomorphic-git reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.
Published: 2026-11-03
Score: 4.3 Medium
EPSS: n/a
KEV: No
Impact: n/a
Action: n/a
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History

Tue, 03 Nov 2026 20:00:00 +0000

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 reads a server-controlled targetSize while applying a packfile delta in src/utils/applyDelta.js and passes it without a bound to Buffer.alloc(targetSize). A malicious or man-in-the-middle-controlled remote can send one delta header that causes git.clone() or git.fetch() to allocate approximately 2 GB before validating the actual delta output. GitPackIndex.fromPack swallows the later size-mismatch error, so a host with sufficient memory may retain the resource waste without a visible failure, while containers, serverless functions, and small virtual machines may terminate. Node.js heap limits do not mitigate the off-heap Buffer allocation. This issue is fixed in version 1.38.6.
Title isomorphic-git: Unbounded memory allocation from attacker-controlled delta target size (DoS)
Weaknesses CWE-400
CWE-789
References
Metrics cvssV3_1

{'score': 4.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L'}

Subscriptions

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-11-03T19:44:06.908Z

Reserved: 2026-07-16T21:37:45.769Z

Link: CVE-2026-63476

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Deferred

Published: 2026-11-03T20:18:16.063

Modified: 2026-11-03T20:18:16.200

Link: CVE-2026-63476

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.

Weaknesses
  • CWE-400

    Uncontrolled Resource Consumption

  • CWE-789

    Memory Allocation with Excessive Size Value