CVE-2026-53587: LIBGIT2

High severity, CVSS 7.5. EPSS: 0.5% chance of exploitation in the next 30 days.

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: before 1.8.6 (fixed in 1.8.6); from 1.9.0, before 1.9.5 (fixed in 1.9.5)

Published 2026-08-20. Last modified 2026-09-09.