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Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M

CVE-2026-53585libgit2: Unbounded Memory Allocation via Delta Object Result-Size Header

Medium 5.3

In plain English

A medium-severity resource allocation without limits in libgit2 from libgit2. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.4%top 66.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official 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, 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Alpine:v3.23libgit21.9.6-r0ALPINE-CVE-2026-53585
Alpine:v3.24libgit21.9.6-r0ALPINE-CVE-2026-53585
Debian:12libgit21.5.1+ds-1+deb12u2DEBIAN-CVE-2026-53585
Debian:13libgit21.9.0+ds-2+deb13u1DEBIAN-CVE-2026-53585
Debian:14libgit21.9.6+ds-1DEBIAN-CVE-2026-53585
Ubuntu:24.04:LTSlibgit21.7.2+ds-1ubuntu3.1UBUNTU-CVE-2026-53585
Ubuntu:26.04:LTSlibgit21.9.1+ds-1ubuntu1.1UBUNTU-CVE-2026-53585

Affected products (as reported)

VendorProductVersions
libgit2 libgit2 < 1.8.6>= 1.9.0, < 1.9.5

Weakness: CWE-770 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References