CVE-2026-63476— isomorphic-git: Unbounded memory allocation from attacker-controlled delta target size (DoS)

Quick assessment

Affected

isomorphic-git isomorphic-git

Exploitation

No confirmed in-the-wild exploitation; assess based on exposure

Recommended action

Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

isomorphic-git 是一个专为 Node.js 和浏览器环境设计的纯 JavaScript 实现的 Git 工具。在 1.38.6 版本之前，该库在中应用 packfile 差异（delta）时，会读取由服务器控制的目标大小（targetSize），并在未进行任何边界检查的情况下，直接将其传递给。攻击者或中间人控制的远程仓库可发送一个恶意构造的差异头（delta header），导致或在验证实际差异输出之前，预先分配约 2 GB 的内存。由于方法会静默忽略后续出现的大小不匹配错误，因此内存充足

CVSS 4.3 · Medium Updated Nov 04, 2026

Possible ATT&CK Techniques 1 AI

T1203 · Exploitation for Client Execution

Get alerts for future matching vulnerabilities Log in to subscribe

Vulnerability Information

Have questions about the vulnerability? See if Shenlong's analysis helps!

View Shenlong Deep Dive ↗

Although we use advanced large model technology, its output may still contain inaccurate or outdated information.Shenlong tries to ensure data accuracy, but please verify and judge based on the actual situation.

Vulnerability Title

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

Source: CVE Program / CVE List V5

Vulnerability 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.

Source: CVE Program / CVE List V5

CVSS Information

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

Source: CVE Program / CVE List V5

Vulnerability Type

未加控制的资源消耗(资源穷尽)

Source: CVE Program / CVE List V5

Affected Products

Vendor	Product	Affected Versions	CPE	Subscribe
isomorphic-git	isomorphic-git	< 1.38.6	-

II. Public POCs for CVE-2026-63476

#	POC Description	Source Link	Shenlong Link

AI-Generated POC Premium

No public POC found.

III. Intelligence Information for CVE-2026-63476

请登录查看更多情报信息。

Other References for CVE-2026-63476 (4)

https://github.com/isomorphic-git/isomorphic-git/pull/2370 x_refsource_MISC
https://github.com/isomorphic-git/isomorphic-git/releases/tag/v1.38.6 x_refsource_MISC
https://github.com/isomorphic-git/isomorphic-git/security/advisories/GHSA-9x82-4j54-863h x_refsource_CONFIRM
https://github.com/isomorphic-git/isomorphic-git/commit/823843d1cd19182df79bc907c767f5bcecb39a0b x_refsource_MISC

https://www.cve.org/CVERecord?id=CVE-2026-63476

Same Patch Batch · isomorphic-git · 2026-11-03 · 4 CVEs total

CVE-2026-63395	8.8 HIGH	isomorphic-git: Arbitrary file write outside the working tree via a directory symlink duri
CVE-2026-63478	5.3 MEDIUM	isomorphic-git: Path traversal via a ".." tree-entry name writes files outside the working
CVE-2026-63475	4.3 MEDIUM	isomorphic-git: Circular symbolic references cause non-terminating resolution (DoS)

IV. Related Vulnerabilities

Same product: isomorphic-git

Same vendor: isomorphic-git

Same weakness: CWE-400