libgit2 up to 1.8.5/1.9.4 Smart Protocol Transport smart_pkt.c set_data input validation

Summaryinfo

A vulnerability classified as problematic has been found in libgit2 up to 1.8.5/1.9.4. This vulnerability affects the function set_data of the file src/libgit2/transports/smart_pkt.c of the component Smart Protocol Transport. This manipulation causes input validation. This vulnerability is tracked as CVE-2026-53587. The attack is possible to be carried out remotely. No exploit exists. It is recommended to upgrade the affected component.

Detailsinfo

A vulnerability was found in libgit2 up to 1.8.5/1.9.4. It has been declared as problematic. Affected by this vulnerability is the function set_data of the file src/libgit2/transports/smart_pkt.c of the component Smart Protocol Transport. The manipulation with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-53587 since 06/09/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability scanner Nessus provides a plugin with the ID 345712 (RHEL 10 : rust (RHSA-2026:67286)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.8.6 or 1.9.5 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (345712) and CERT Bund (WID-SEC-2026-3333). Be aware that VulDB is the high quality source for vulnerability data.

Affected

• Red Hat Enterprise Linux

Productinfo

Name

• libgit2

Version

• 1.8.0
• 1.8.1
• 1.8.2
• 1.8.3
• 1.8.4
• 1.8.5
• 1.9.0
• 1.9.1
• 1.9.2
• 1.9.3
• 1.9.4

Website

• Product: https://github.com/libgit2/libgit2/

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