CVE-2026-53583: libgit2: Inverted IP SubjectAltName Comparison in OpenSSL Backend
CSIRTS triage
- What
- The OpenSSL backend in libgit2 performs inverted IP SubjectAltName comparison during TLS certificate validation, allowing authentication bypass.
- Who is affected
- Systems using libgit2 with OpenSSL for TLS connections to remote Git repositories.
- Urgency
- Medium severity (CVSS 6.5) and not yet exploited; deploy patches in the next update cycle.
- Action
- Upgrade libgit2 to a version with corrected certificate validation logic for IP addresses in SubjectAltName fields.
AI-assisted analysis generated from the source advisory — verify against the original.
⚡ Watch libgit2
Get an email when a new libgit2 advisory drops — max one per day, one-click unsubscribe.
Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-53583
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-535830.24% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 15% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-53583 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
More from Microsoft Security Response Center
- lowCVE-2026-14673: PostgreSQL amcheck does not clear untrusted search path2026-08-11
- criticalCVE-2026-69836: Microsoft Entra ID Remote Code Execution Vulnerability2026-08-11
- mediumCVE-2026-53792: rsync < 3.5.0 Out-of-Bounds Read via Zero-Length Checksum Block2026-08-11
- highCVE-2026-70347: Windows Installer Elevation of Privilege Vulnerability2026-08-11
- highCVE-2026-64909: Microsoft Office Remote Code Execution Vulnerability2026-08-11