ALAS2023-2026-2083

References: CVE-2026-53583  CVE-2026-53584  CVE-2026-53585  CVE-2026-53586  CVE-2026-53587  CVE-2026-5917 
FAQs regarding Amazon Linux ALAS/CVE Severity

Issue Overview:

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)

Issue Correction:
Run dnf update libgit2 --releasever 2023.12.20260831 or dnf update --advisory ALAS2023-2026-2083 --releasever 2023.12.20260831 to update your system.
More information on how to update your system can be found on this page: Amazon Linux 2023 documentation

New Packages:

aarch64:
    libgit2-debuginfo-1.6.4-116.amzn2023.aarch64
    libgit2-1.6.4-116.amzn2023.aarch64
    libgit2-devel-1.6.4-116.amzn2023.aarch64
    libgit2-debugsource-1.6.4-116.amzn2023.aarch64

src:
    libgit2-1.6.4-116.amzn2023.src

x86_64:
    libgit2-debuginfo-1.6.4-116.amzn2023.x86_64
    libgit2-1.6.4-116.amzn2023.x86_64
    libgit2-devel-1.6.4-116.amzn2023.x86_64
    libgit2-debugsource-1.6.4-116.amzn2023.x86_64