CVE-2026-63476

isomorphic-git is a pure JavaScript implementation of Git for Node.js and browsers

Risk score: 40/100
CVSS: 4.3 v3.1
Exploit chance (30 days): 0.3%
Published: 3 Nov 2026

Open in the live forecast Today's forecast

What to know

What it is: 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 remo…
Affected: See advisory
Fix: Upgrade the product to 1.38.6 or later.
Exploitation: No known exploitation

Why it is Yellow

CVSS 4.3 medium
On your watchlist: node.js

References

Original 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.

Last activity 3 Nov 2026. Patch Forecast updates every hour.