Vulnerability details

CVE-2026-53587

libgit2 libgit2

libgit2 - Unauthenticated network-reachable heap out-of-bounds read in transports/smart_pkt.c:set_data

CVSS 3.1

7.5High

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, 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 scores

Score	Version	Source	Vector
7.5High	3.1	CVEProject cvelistV5 (CNA) (GitHub_M)	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`

Affected products

Vendor	Product	Versions	Source
libgit2	libgit2	< 1.8.6	CVEProject cvelistV5 (CNA)
libgit2	libgit2	>= 1.9.0, < 1.9.5	CVEProject cvelistV5 (CNA)

References and advisories

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

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Details

Published: 2026-08-20
Last updated: 2026-08-20
State: Published
Assigner (CNA): GitHub_M

Exploit prediction (EPSS)

0.47%

Probability of exploitation in 30 days

40.9%

Percentile (among all CVEs)

SSVC assessment (CISA)

Automatable: Yes
Exploitation: Proof of concept
Technical impact: Partial

Weaknesses (CWE)

CWE-20
Improper Input Validation
CWE-125
Out-of-bounds Read
CWE-126
Buffer Over-read
CWE-1284
Improper Validation of Specified Quantity in Input