CVE-2026-55199

Name
CVE-2026-55199
Description
libssh2 through 1.11.1, fixed in commit 1762685, contains a pre-authentication denial of service vulnerability in the SSH_MSG_EXT_INFO handler in src/packet.c that allows a malicious SSH server to cause a client CPU exhaustion loop by sending a crafted extension count value. A malicious server can set nr_extensions to 0xFFFFFFFF during key exchange, causing the client to spin in a tight CPU loop for over 60 seconds because return values from _libssh2_get_string() are unchecked and the session timeout does not apply to CPU-bound loops.
NVD Severity
unknown
Other trackers
CVE, NVD, CERT, CVE Details, CIRCL, Arch Linux, Debian, Red Hat, Ubuntu, Gentoo, SUSE (Bugzilla), SUSE (CVE), Mageia
Mailing lists
oss-security, full-disclosure, bugtraq
Exploits
Exploit DB, Metasploit
Forges
GitHub (code, issues), Aports (code, issues)

References

Type URI
disclosure@vulncheck.com https://github.com/libssh2/libssh2/commit/17626857d20b3c9a1addfa45979dadcee1cd84a4
disclosure@vulncheck.com https://github.com/libssh2/libssh2/pull/1864
disclosure@vulncheck.com https://www.vulncheck.com/advisories/libssh2-pre-authentication-dos-via-ssh-msg-ext-info-handler

Match rules

CPE URI Source package Min version Max version
cpe:2.3:a:libssh2:libssh2:*:*:*:*:*:*:*:* libssh2 >= None <= 1.11.1

Vulnerable and fixed packages

Source package Branch Version Maintainer Status
rust edge-main 1.96.1-r0 team/rust <alpine@ptrcnull.me> fixed
libssh2 edge-main 1.11.1-r3 Natanael Copa <ncopa@alpinelinux.org> fixed
libssh2 edge-main 1.11.1-r2 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 edge-main 1.11.1-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 edge-main 1.11.1-r0 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 edge-main 1.11.0-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 edge-main 1.9.0-r2 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 edge-main 1.9.0-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 edge-main 1.9.0-r0 None possibly vulnerable
libssh2 edge-main 1.8.1-r0 None possibly vulnerable
libssh2 3.24-main 1.11.1-r3 Natanael Copa <ncopa@alpinelinux.org> fixed
libssh2 3.24-main 1.11.1-r2 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.23-main 1.11.1-r3 Natanael Copa <ncopa@alpinelinux.org> fixed
libssh2 3.23-main 1.11.1-r2 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.23-main 1.11.1-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.22-main 1.11.1-r2 Natanael Copa <ncopa@alpinelinux.org> fixed
libssh2 3.22-main 1.11.1-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.22-main 1.11.1-r0 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.22-main 1.11.0-r1 None possibly vulnerable
libssh2 3.22-main 1.9.0-r1 None possibly vulnerable
libssh2 3.22-main 1.9.0-r0 None possibly vulnerable
libssh2 3.22-main 1.8.1-r0 None possibly vulnerable
libssh2 3.21-main 1.11.1-r2 Natanael Copa <ncopa@alpinelinux.org> fixed
libssh2 3.21-main 1.11.1-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.21-main 1.11.1-r0 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.21-main 1.11.0-r1 None possibly vulnerable
libssh2 3.21-main 1.9.0-r1 None possibly vulnerable
libssh2 3.21-main 1.9.0-r0 None possibly vulnerable
libssh2 3.21-main 1.8.1-r0 None possibly vulnerable
libssh2 3.20-main 1.11.0-r3 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.20-main 1.11.0-r2 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.20-main 1.11.0-r1 None possibly vulnerable
libssh2 3.20-main 1.9.0-r1 None possibly vulnerable
libssh2 3.20-main 1.9.0-r0 None possibly vulnerable
libssh2 3.20-main 1.8.1-r0 None possibly vulnerable
libssh2 3.19-main 1.11.0-r1 Natanael Copa <ncopa@alpinelinux.org> possibly vulnerable
libssh2 3.19-main 1.9.0-r1 None possibly vulnerable
libssh2 3.19-main 1.9.0-r0 None possibly vulnerable
libssh2 3.19-main 1.8.1-r0 None possibly vulnerable