# CVE-2026-53587

## Summary

- **CVE ID:** CVE-2026-53587
- **Severity:** HIGH
- **CVSS Score:** 7.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-20, CWE-125, CWE-126, CWE-1284
- **Published:** Aug 20, 2026
- **Last Modified:** Aug 20, 2026

## 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, libgit2 performs a fixed-size strncmp in set_data in src/libgit2/transports/smart_pkt.c without first verifying that the smart-protocol pkt-line capability buffer contains 14 bytes. A malicious Git server can make bytes after the pkt-line complete object-format=, causing format_str to advance beyond the pkt-line and the following memchr length calculation to underflow. The resulting heap out-of-bounds walk can crash a client during the first refs-advertisement packet over HTTP, HTTPS, SSH, or the Git protocol. This issue is fixed in versions 1.8.6 and 1.9.5.

## Affected Products

- libgit2 — libgit2 (< 1.8.6)
- libgit2 — libgit2 (>= 1.9.0, < 1.9.5)

## References

- [CNA](https://github.com/libgit2/libgit2/security/advisories/GHSA-pm24-4jhq-3xvm)
- [CNA](https://github.com/libgit2/libgit2/commit/2c0ce8c0132ac38ab0db28239462a671e2e5440e)
- [CNA](https://github.com/libgit2/libgit2/commit/affda60c10fcef16723451c0d7dc71b71dc20ad3)
- [CNA](https://github.com/libgit2/libgit2/commit/d7a9fb87f504434e9f45228678953c4fa56e7640)
- [CNA](https://github.com/libgit2/libgit2/releases/tag/v1.8.6)
- [CNA](https://github.com/libgit2/libgit2/releases/tag/v1.9.5)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.47%
- **EPSS Percentile:** 39.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._