6.5

CVE-2026-53583: libgit2 Improper Certificate Validation

CVSS: 6.5v3.1MediumAwaiting analysis
AliasesUBUNTU-CVE-2026-53583USN-8907-1DEBIAN-CVE-2026-53583
Published 20-08-2026Last modified 20-08-2026
Open JSON

Vulnerability summary

CVE-2026-53583 is a medium (CVSS 6.5) Improper Certificate Validation vulnerability in libgit2. EPSS estimates a 0.24% chance of exploitation in the next 30 days, higher than 14% of scored vulnerabilities.

Overall risk
26/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.24%
0%100%
Low · +0.05 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2 · Related 1
OPENSUSE-SU-2026:11315-1RHSA-2026:59361

Timeline

  1. 20-08-2026
    PublishedVulnerability first disclosed.
  2. 20-08-2026
    Last modifiedVulnerability information updated.

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, 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.

CVSS metrics

4 scores · 4 sources · 1 version

EPSS trend

Probability

0.24%

Chance of exploitation in the next 30 days

Percentile

14%

Versus all other CVEs

30-day change

+0.05 pp

From 0.19% on 21-09-2026

21-09-202621-10-2026
EPSS score
0.24%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Debian1 product
  • libgit2< 1.9.0+ds-2+deb13u1 | < 1.9.6+ds-1
Libgit21 product
  • libgit2< 1.8.6 | ≥ 1.9.0, < 1.9.5
Ubuntu1 product
  • libgit2All versions (No fix recorded) | < 1.7.2+ds-1ubuntu3.3 | < 1.9.1+ds-1ubuntu1.3

3 vendors · 3 products

References

11 links
Show all 11 references