Medium [CVE-2026-53583] Network attacker can intercept HTTPS connections via inverted IP SubjectAltName comparison
This medium-severity Red Hat Linux advisory covers CVE-2026-53583 affecting Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8.
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Summary
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. An inverted comparison in the OpenSSL backend's certificate verification logic, specifically when handling IP-literal hosts and certificate IP SubjectAltNames, allows a network attacker to intercept HTTPS connections.
By presenting a CA-trusted certificate with any IP SubjectAltName, an attacker can trick libgit2 into accepting a mismatched IP address, leading to the interception of sensitive communication. Red Hat severity: Moderate — CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N).
Weakness: CWE-295.
- < 1.8.6
- < 1.9.5
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
- 1.8.6
- 1.9.5
- libgit2-main-1.9.7-1.hum1
- RHSA-2026:59361
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 13 days ago·verify at source
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