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Vulnerability record · CVE-2026-53587 · published 20 August 2026

CVE-2026-53587: Improper input validation vulnerability

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, libgit2 performs a fixed-size strncmp in set_data in src/libgit2/transports/smart_pkt.c without first verifying that the smart-protocol pkt-line capability buffer contains 14 bytes. A malicious Git server can make bytes after the pkt-line complete object-format=, causing format_str to advance beyond the pkt-line and the following memchr length calculation to underflow. The resulting heap out-of-bounds walk can crash a client during the first refs-advertisement packet over HTTP, HTTPS, SSH, or the Git protocol. This issue is fixed in versions 1.8.6 and 1.9.5.

7.5 CVSS 3.1 High EPSS 0.68% · top 49.4% CWE-20 · Improper input validationCWE-125 · Out-of-bounds read Awaiting Analysis
7.5CVSS 3.1 base score
0.68%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
7References
9 Sep 2026Last modified by NVD

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, libgit2 performs a fixed-size strncmp in set_data in src/libgit2/transports/smart_pkt.c without first verifying that the smart-protocol pkt-line capability buffer contains 14 bytes. A malicious Git server can make bytes after the pkt-line complete object-format=, causing format_str to advance beyond the pkt-line and the following memchr length calculation to underflow. The resulting heap out-of-bounds walk can crash a client during the first refs-advertisement packet over HTTP, HTTPS, SSH, or the Git protocol. This issue is fixed in versions 1.8.6 and 1.9.5.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

LinkTags
https://github.com/libgit2/libgit2/commit/2c0ce8c0132ac38ab0db28239462a671e2e5440e
https://github.com/libgit2/libgit2/commit/affda60c10fcef16723451c0d7dc71b71dc20ad3
https://github.com/libgit2/libgit2/commit/d7a9fb87f504434e9f45228678953c4fa56e7640
https://github.com/libgit2/libgit2/releases/tag/v1.8.6
https://github.com/libgit2/libgit2/releases/tag/v1.9.5
https://github.com/libgit2/libgit2/security/advisories/GHSA-pm24-4jhq-3xvm
https://github.com/libgit2/libgit2/security/advisories/GHSA-pm24-4jhq-3xvm

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Source: NIST National Vulnerability Database (record CVE-2026-53587), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.