CVE-2026-55199
Fixed in a distro release EPSS <1%CVSS 5.9
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.
Products: libssh2
Distro releases
| Release | Package | Fixed in |
|---|---|---|
| Alpine 3.21 | libssh2 | 1.11.1-r2 |
| Alpine 3.22 | libssh2 | 1.11.1-r2 |
| Alpine 3.23 | libssh2 | 1.11.1-r3 |
| Alpine 3.24 | libssh2 | 1.11.1-r3 |
| Alpine 3.24 | rust | 1.96.1-r0 |
| Chainguard | libssh2 | 1.11.1-r7 |
| Chainguard | libssh2-dev | 1.11.1-r7 |
| Chainguard | libssh2-doc | 1.11.1-r7 |
| Debian 13 | libssh2 | 1.11.1-1+deb13u1 |
| Debian 14 | libssh2 | 1.11.1-4 |
| Red Hat hummingbird 1 | libssh2 | 0:1.11.1-8.hum1 |
| Red Hat hummingbird 1 | libssh2-devel | 0:1.11.1-8.hum1 |
| Red Hat hummingbird 1 | libssh2-docs | 0:1.11.1-8.hum1 |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS | libssh2_org | 1.11.0-150000.4.32.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | libssh2_org | 1.11.0-150000.4.32.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Micro 5.3 | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Micro 5.4 | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Micro 5.5 | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Module for Basesystem 15 SP7 | libssh2_org | 1.11.0-150600.20.3.1 |
| SUSE Linux Enterprise Server 12 SP5-LTSS | libssh2_org | 1.11.0-29.18.1 |
| SUSE Linux Enterprise Server 15 SP4-LTSS | libssh2_org | 1.11.0-150000.4.32.1 |
| SUSE Linux Enterprise Server 15 SP4-LTSS | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Server 15 SP5-LTSS | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Server 15 SP6-LTSS | libssh2_org | 1.11.0-150600.20.3.1 |
| SUSE Linux Enterprise Server 16.0 | libssh2_org | 1.11.1-160000.4.1 |
| SUSE Linux Enterprise Server LTSS Extended Security 12 SP5 | libssh2_org | 1.11.0-29.18.1 |
| SUSE Linux Enterprise Server for SAP Applications 15 SP4 | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Server for SAP Applications 15 SP5 | libssh2_org | 1.11.0-150200.9.5.1 |
| SUSE Linux Enterprise Server for SAP Applications 15 SP6 | libssh2_org | 1.11.0-150600.20.3.1 |
| SUSE Linux Enterprise Server for SAP applications 16.0 | libssh2_org | 1.11.1-160000.4.1 |
| SUSE Linux Micro 6.0 | libssh2_org | 1.11.0-3.1 |
| SUSE Linux Micro 6.1 | libssh2_org | 1.11.0-slfo.1.1_2.1 |
| SUSE Linux Micro 6.2 | libssh2_org | 1.11.1-160000.4.1 |
| Ubuntu 24.04 LTS | libssh2 | 1.11.0-4.1ubuntu0.24.04.2 |
| Ubuntu 25.10 | libssh2 | 1.11.1-1ubuntu0.25.10.2 |
| Ubuntu 26.04 LTS | libssh2 | 1.11.1-1ubuntu0.26.04.2 |
| Wolfi | libssh2 | 1.11.1-r7 |
| Wolfi | libssh2-dev | 1.11.1-r7 |
| Wolfi | libssh2-doc | 1.11.1-r7 |
| openSUSE Leap 16.0 | libssh2_org | 1.11.1-160000.4.1 |
| openSUSE Tumbleweed | libssh2_org | 1.11.1-3.1 |