Amazon Linux 2023 : libgit2, libgit2-devel (ALAS2023-2026-2083)

high Nessus Plugin ID 341845

Synopsis

The remote Amazon Linux 2023 host is missing a security update.

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-2083 advisory.

libgit2 Inverted IP SubjectAltName Comparison in OpenSSL Backend ( vuln_1_1_1 ) (CVE-2026-53583)

libgit2 Submodule path traversal (CVE-2026-53584)

Unbounded Memory Allocation via Delta Object Result-Size Header (CVE-2026-53585)

libgit2's builtin HTTP transport follows offsite redirects for the initial smart HTTP request by default.
If the redirected server then returns 401 Unauthorized, libgit2 asks the application credential callback for credentials using the original remote URL, not the redirected URL. The returned credential is then attached to the next request to the redirected host as an Authorization header. (CVE-2026-53586)

libgit2 version 1.9.4 and below is vulnerable to a heap out-of-bounds read in set_data() in src/libgit2/transports/smart_pkt.c.

The vulnerable code uses a fixed-size strncmp (smart_pkt.c:239) against the unvalidated capability buffer of a smart-protocol pkt-line. When the bytes following the pkt-line in the contiguous receive buffer happen to continue with ct-format=, the comparison spuriously matches, advancing format_str past the pkt-line boundary. The following memchr(format_str, ' ', len - (format_str - line)) (smart_pkt.c:246) then underflows its size_t size argument to ~SIZE_MAX and walks the heap looking for a space byte. An unauthenticated remote attacker who controls (or man-in-the-middles) a Git server reached over HTTP/HTTPS/SSH/git:// can trigger this on the FIRST ref-pkt of the refs advertisement, before any capability negotiation has taken place. The OOB walk causes a process crash (SIGSEGV) when memchr enters an unmapped page, and -- on heap layouts where memchr finds a stray space byte before crashing -- can additionally drive the git_error_set(...'%.*s', format_len, format_str) formatter to copy a large window of heap memory into the error string. (CVE-2026-53587)

libgit2 versions v0.27.0 through v1.9.0 built with the libssh2 SSH backend (USE_SSH=libssh2) contain a shell command injection vulnerability that allows remote attackers to execute arbitrary commands on an SSH server by supplying a repository path containing unescaped shell metacharacters such as single quotes, semicolons, or pipes. The gen_proto() function in ssh_libssh2.c inserts the repository path directly into a shell command string without escaping special characters before passing it to libssh2_channel_exec(), enabling an attacker to craft a malicious submodule URL in a .gitmodules file that, when processed during a recursive clone, causes the remote server's shell to interpret injected commands under the victim's SSH user account. (CVE-2026-5917)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'dnf update libgit2 --releasever 2023.12.20260831' or or 'dnf update --advisory ALAS2023-2026-2083 --releasever 2023.12.20260831' to update your system.

Plugin Details

Severity: High

ID: 341845

File Name: al2023_ALAS2023-2026-2083.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 8/31/2026

Updated: 8/31/2026

Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Nessus Agent, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.9

Percentile: 58.17

CVSS v2

Risk Factor: Critical

Base Score: 10

Temporal Score: 7.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C

CVSS Score Source: CVE-2026-5917

CVSS v3

Risk Factor: Medium

Base Score: 6.5

Temporal Score: 5.7

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

CVSS Score Source: CVE-2026-53586

CVSS v4

Risk Factor: High

Base Score: 8.6

Threat Score: 6.1

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:libgit2-debuginfo, p-cpe:/a:amazon:linux:libgit2-debugsource, p-cpe:/a:amazon:linux:libgit2-devel, p-cpe:/a:amazon:linux:libgit2

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 8/31/2026

Vulnerability Publication Date: 7/23/2026

Reference Information

CVE: CVE-2026-53583, CVE-2026-53584, CVE-2026-53585, CVE-2026-53586, CVE-2026-53587, CVE-2026-5917

Detections

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