isomorphic-git: Unbounded memory allocation from attacker-controlled delta target size (DoS)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-63476
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-03 20:18:16 UTC
Updated2026-11-03 20:18:16 UTC
Descriptionisomorphic-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.

Risk And Classification

Primary CVSS: v3.1 4.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Problem Types: CWE-400 | CWE-789 | CWE-400 CWE-400: Uncontrolled Resource Consumption | CWE-789 CWE-789: Memory Allocation with Excessive Size Value

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
3.1CNADECLARED4.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Isomorphic-git Isomorphic-git affected < 1.38.6 Not specified

References

ReferenceSourceLinkTags
github.com/isomorphic-git/isomorphic-git/pull/2370 [email protected] github.com
github.com/isomorphic-git/isomorphic-git/releases/tag/v1.38.6 [email protected] github.com
github.com/isomorphic-git/isomorphic-git/security/advisories/GHSA-9x82-4... [email protected] github.com
github.com/isomorphic-git/isomorphic-git/commit/823843d1cd19182df79bc907... [email protected] github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

© CVE.report 2026

Use of this information constitutes acceptance for use in an AS IS condition. There are NO warranties, implied or otherwise, with regard to this information or its use. Any use of this information is at the user's risk. It is the responsibility of user to evaluate the accuracy, completeness or usefulness of any information, opinion, advice or other content. EACH USER WILL BE SOLELY RESPONSIBLE FOR ANY consequences of his or her direct or indirect use of this web site. ALL WARRANTIES OF ANY KIND ARE EXPRESSLY DISCLAIMED. This site will NOT BE LIABLE FOR ANY DIRECT, INDIRECT or any other kind of loss.

CVE, CWE, and OVAL are registred trademarks of The MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. This site includes MITRE data granted under the following license.

Free CVE JSON API cve.report/api

CVE.report and Source URL Uptime Status status.cve.report