CVE-2026-53583: LIBGIT2

Medium severity, CVSS 6.5. EPSS: 0.2% 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, verify_server_cert in src/libgit2/streams/openssl.c uses an inverted !!memcmp result in the GEN_IPADD branch when comparing an IP-literal host with a certificate IP SubjectAltName. OpenSSL builds reject matching IP addresses and accept mismatched IP addresses, allowing a network attacker with a CA-trusted certificate containing any IP SubjectAltName to intercept libgit2 connections to IP-literal HTTPS URLs. DNS SubjectAltName validation and non-OpenSSL TLS backends are not affected. 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.