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Fencer Vulns
medium 6.5

CVE-2026-53583 json

libgit2: Inverted IP SubjectAltName Comparison in OpenSSL Backend

published 2026-08-20 2 mo ago modified 2026-10-26 13 d ago also EUVD-2026-63549 , JLSEC-2026-1369

cvss
6.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 14%
public exploits
0
none known

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.

Patch / fix

  • julia LibGit2_jll 1.9.6+0
  • libgit2 libgit2 1.8.6, 1.9.5
  • libgit2 Debian 13 1.9.0+ds-2+deb13u1
  • libgit2 Debian 14 1.9.6+ds-1

debian advisories DEBIAN-CVE-2026-53583

  • libgit2 Ubuntu 24.04 LTS 1.7.2+ds-1ubuntu3.3
  • libgit2 Ubuntu 26.04 LTS 1.9.1+ds-1ubuntu1.3

ubuntu advisories UBUNTU-CVE-2026-53583

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libgit2 hummingbird 1 1.9.7-1.hum1

red hat advisories RHSA-2026:59361

  • libgit2 openSUSE Tumbleweed 1.9.6-1.1

opensuse advisories openSUSE-SU-2026:11315-1

  • libgit2 Alpine 3.24, Alpine 3.23 1.9.6-r0

alpine advisories ALPINE-CVE-2026-53583

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • libgit2 Azure Linux 3.0 1.7.2-3

azure linux advisories AZL-96971

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-53583 updated cvss 6.5

libgit2: libgit2: Network attacker can intercept HTTPS connections via inverted IP SubjectAltName comparison

  • Red Hat Enterprise Linux 8 libgit2 Red Hat Enterprise Linux 9 rust, cargo, clippy, rustfmt, rust-gdb, rust-src, +8 more Red Hat Enterprise Linux 10 rust Red Hat Enterprise Linux AI (RHEL AI) 3 rust, libgit2
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images libgit2 1.9.7-1.hum1
    fixed: vendor fix RHSA-2026:59361

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2 mo ago

Exploit prediction

0.24% chance of exploitation in the next 30 days, higher than 14% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/libgit2/libgit2/security/advisories/GHSA-h7gc-w2gg-p9xp referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
OSV 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
julia LibGit2_jll
<1.9.6+0
1.9.6+0

Affected products

  • libgit2 libgit2

Classification

Weakness
  • CWE-295 Improper Certificate Validation
  • CWE-297 Improper Validation of Certificate with Host Mismatch

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.