CVE-2026-53587Public exploitNetwork attack vector

Client crash via unchecked pkt-line capability length

Published Aug 20, 2026 · Updated Aug 20, 2026

Out-of-bounds read in libgit2 before 1.8.6 and 1.9.5 allows remote attackers to crash a client via a crafted refs advertisement. In set_data in src/libgit2/transports/smart_pkt.c, libgit2 tests the capability buffer for object-format= with a fixed 14-byte comparison before confirming that 14 bytes remain in the current pkt-line, then underflows the following memchr length when format_str advances past the pkt-line boundary. Exposure is pre-auth over HTTP, HTTPS, SSH, or git:// for applications that clone, fetch, or list refs from an attacker-controlled or man-in-the-middle Git server, and the published proof of concept demonstrates a process crash on the first refs-advertisement packet.

CVSS severity7.5
High
EPSS probability0.47%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in libgit2 before 1.8.6 and 1.9.5 allows remote attackers to crash a client via a crafted refs advertisement. In set_data in src/libgit2/transports/smart_pkt.c, libgit2 tests the capability buffer for object-format= with a fixed 14-byte comparison before confirming that 14 bytes remain in the current pkt-line, then underflows the following memchr length when format_str advances past the pkt-line boundary. Exposure is pre-auth over HTTP, HTTPS, SSH, or git:// for applications that clone, fetch, or list refs from an attacker-controlled or man-in-the-middle Git server, and the published proof of concept demonstrates a process crash on the first refs-advertisement packet.

The record

CVE
CVE-2026-53587
Published
Aug 20, 2026
Updated
Aug 20, 2026
Vendor
libgit2
Product
libgit2
Classifications
CWE-1284, CWE-125, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.8.6
  2. Affected versionversion=>= 1.9.0, < 1.9.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

libgit2 · libgit2version=< 1.8.6; version=>= 1.9.0, < 1.9.5

Published CVSS scores

7.5GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1284Improper Validation of Specified Quantity in Input
CWE-125Out-of-bounds Read
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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