Bug 2520693 (CVE-2026-53587)

Summary: CVE-2026-53587 libgit2: libgit2: Denial of Service due to heap out-of-bounds read from malicious Git server
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: bbrownin, rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in libgit2. A fixed-size string comparison in the `set_data` function within `transports/smart_pkt.c` does not adequately verify the size of a network packet buffer. A remote attacker, operating a malicious Git server, can send a specially crafted packet-line capability buffer. This can lead to a heap out-of-bounds read, causing the client application to crash and resulting in a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2521756, 2521757, 2521754, 2521755    
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Description OSIDB Bzimport 2026-08-20 19:02:38 UTC 
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.