Bug 2520696 (CVE-2026-53585)

Summary: CVE-2026-53585 libgit2: libgit2: Denial of Service via Unbounded Memory Allocation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
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. The `git_delta_apply` function incorrectly trusts an attacker-controlled size value from a delta object header, which is used for memory allocation before proper validation of delta instructions. A remote attacker or local user can supply malicious pack data, for example, through `git_clone` or `git_fetch`, to trigger extremely large memory allocations. This can lead to the exhaustion of system memory, 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: 2521746, 2521748, 2521749, 2521747    
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Description OSIDB Bzimport 2026-08-20 19:02:44 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, git_delta_apply in src/libgit2/delta.c trusts the attacker-controlled res_sz value parsed by hdr_sz from a delta object header and passes that amount to git__malloc before validating delta instructions. Malicious pack data supplied through git_clone, git_fetch, git_remote_fetch, git_indexer_append, or a local attacker-supplied repository can use a very small multi-level OFS_DELTA chain to retain extremely large allocations and exhaust memory. This issue is fixed in versions 1.8.6 and 1.9.5.