CVE-2026-55200

EUVD-2026-37784
libssh2 through 1.11.1, fixed in commit 7acf3df contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.
ProviderTypeBase ScoreAtk. VectorAtk. ComplexityPriv. RequiredVector
NISTPrimary
8.1 HIGH
NETWORK
HIGH
NONE
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Base Score
CVSS 3.x
EPSS Score
Percentile: 79%
Affected Products (NVD)
VendorProductVersion
libssh2libssh2
𝑥
≤ 1.11.1
𝑥
= Vulnerable software versions
Debian logo
Debian Releases
Debian Product
Codename
libssh2
bookworm
vulnerable
bullseye
vulnerable
forky
1.11.1-5
fixed
sid
1.11.1-5
fixed
trixie
1.11.1-1+deb13u1
fixed
trixie (security)
1.11.1-1+deb13u1
fixed
Ubuntu logo
Ubuntu Releases
Ubuntu Product
Codename
libssh2
bionic
not-affected
focal
not-affected
jammy
not-affected
noble
not-affected
questing
Fixed 1.11.1-1ubuntu0.25.10.2
released
resolute
Fixed 1.11.1-1ubuntu0.26.04.2
released
trusty
not-affected
Azure Linux logo
Azure Linux Releases
Azure Package
Release
libssh2
Azure Linux 3.0
0:1.11.1-3.azl3
fixed
Common Weakness Enumeration
Vulnerability Media Exposure
References
https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8
https://github.com/libssh2/libssh2/pull/2052
https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c
https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc