CVE catalog
CVE-2026-55199
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 cau
- Severity
- High · CVSS 8.2
- Published
- Source
- [NVD] · [CVE record]
- EPSS
- 0.92% · Oct 25, 2026
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.
Vulnerable and fixed packages
Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.
| Distribution | Package | Release | Version | Status |
|---|---|---|---|---|
| Debian | libssh2 | sid | 1.11.1-6 | fixed |
| Debian | libssh2 | forky | 1.11.1-6 | fixed |
| Debian | libssh2 | trixie | 1.11.1-1+deb13u2 | fixed |
| Debian | libssh2 | trixie-security | 1.11.1-1+deb13u1 | fixed |
| Debian | libssh2 | bookworm | 1.10.0-3 | not affected |
| Debian | libssh2 | bookworm-security | 1.10.0-3+deb12u1 | not affected |
| Cpe | libssh2 | Not reported | 1.11.0-4.1ubuntu0.24.04.2 | fixed |
| Cpe | libssh2-1-dev | Not reported | 1.11.0-4.1ubuntu0.24.04.2 | fixed |
| Cpe | libssh2-1t64 | Not reported | 1.11.0-4.1ubuntu0.24.04.2 | fixed |
| Cpe | libssh2 | Not reported | Not reported | unknown |
| Alpine | libssh2 | 3.21 | 1.11.1-r2 | fixed |
| Alpine | libssh2 | 3.22 | 1.11.1-r2 | fixed |
| Alpine | libssh2 | 3.23 | 1.11.1-r3 | fixed |
| Alpine | libssh2 | 3.24 | 1.11.1-r3 | fixed |
| Alpine | rust | 3.24 | 1.96.1-r0 | fixed |
| Ubuntu | libssh2 | 24.04 | 1.11.0-2 | vulnerable |
| Ubuntu | libssh2 | 24.04 | 1.11.0-3 | vulnerable |
| Ubuntu | libssh2 | 24.04 | 1.11.0-4 | vulnerable |
| Ubuntu | libssh2 | 24.04 | 1.11.0-4.1build1 | vulnerable |
| Ubuntu | libssh2 | 24.04 | 1.11.0-4.1build2 | vulnerable |
| Ubuntu | libssh2 | 24.04 | 1.11.0-4.1ubuntu0.24.04.1 | vulnerable |
| Ubuntu | libssh2 | 24.04 | 1.11.0-4.1ubuntu0.24.04.2 | fixed |
| Ubuntu | libssh2 | 25.10 | 1.11.1-1 | vulnerable |
| Ubuntu | libssh2 | 25.10 | 1.11.1-1build1 | vulnerable |
| Ubuntu | libssh2 | 25.10 | 1.11.1-1ubuntu0.25.10.1 | vulnerable |
| Ubuntu | libssh2 | 25.10 | 1.11.1-1ubuntu0.25.10.2 | fixed |
| Ubuntu | libssh2 | 26.04 | 1.11.1-1build1 | vulnerable |
| Ubuntu | libssh2 | 26.04 | 1.11.1-1build2 | vulnerable |
| Ubuntu | libssh2 | 26.04 | 1.11.1-1ubuntu0.26.04.1 | vulnerable |
| Ubuntu | libssh2 | 26.04 | 1.11.1-1ubuntu0.26.04.2 | fixed |
| Suse | libssh2_org | linux enterprise module for basesystem 15 sp7 | 1.11.0-150600.20.3.1 | fixed |
| Suse | libssh2_org | linux enterprise server 15 sp6-ltss | 1.11.0-150600.20.3.1 | fixed |
| Suse | libssh2_org | linux enterprise server for sap applications 15 sp6 | 1.11.0-150600.20.3.1 | fixed |
| Suse | libssh2_org | linux enterprise high performance computing 15 sp4-espos | 1.11.0-150000.4.32.1 | fixed |
| Suse | libssh2_org | linux enterprise high performance computing 15 sp4-ltss | 1.11.0-150000.4.32.1 | fixed |
| Suse | libssh2_org | linux enterprise server 15 sp4-ltss | 1.11.0-150000.4.32.1 | fixed |
| Suse | libssh2_org | linux enterprise micro 5.3 | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise micro 5.4 | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise micro 5.5 | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise high performance computing 15 sp4-espos | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise high performance computing 15 sp4-ltss | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise high performance computing 15 sp5-espos | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise high performance computing 15 sp5-ltss | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise server 15 sp4-ltss | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise server 15 sp5-ltss | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise server for sap applications 15 sp4 | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux enterprise server for sap applications 15 sp5 | 1.11.0-150200.9.5.1 | fixed |
| Suse | libssh2_org | linux micro 6.0 | 1.11.0-3.1 | fixed |
| Suse | libssh2_org | linux enterprise server 16.0 | 1.11.1-160000.4.1 | fixed |
| Suse | libssh2_org | linux enterprise server for sap applications 16.0 | 1.11.1-160000.4.1 | fixed |
| Suse | libssh2_org | linux micro 6.2 | 1.11.1-160000.4.1 | fixed |
| Opensuse | libssh2_org | leap 16.0 | 1.11.1-160000.4.1 | fixed |
Fixed-version evidence
| Distribution | Package | Type | Release | Fixed version | Urgency | Origin | Bugs |
|---|---|---|---|---|---|---|---|
| Debian | libssh2 | source | sid | 1.11.1-4 | not yet assigned | Not reported | [1140401] |
| Debian | libssh2 | source | forky | 1.11.1-4 | not yet assigned | Not reported | [1140401] |
| Debian | libssh2 | source | trixie | 1.11.1-1+deb13u1 | not yet assigned | Not reported | [1140401] |
| Debian | libssh2 | source | bookworm | Not affected | unimportant | Not reported | [1140401] |
| Cpe | libssh2 | cpe | Not reported | 1.11.0-4.1ubuntu0.24.04.2 | Not reported | Not reported | Not reported |
| Cpe | libssh2-1-dev | cpe | Not reported | 1.11.0-4.1ubuntu0.24.04.2 | Not reported | Not reported | Not reported |
| Cpe | libssh2-1t64 | cpe | Not reported | 1.11.0-4.1ubuntu0.24.04.2 | Not reported | Not reported | Not reported |
| Alpine | libssh2 | apk | 3.21 | 1.11.1-r2 | Not reported | ALPINE-CVE-2026-55199 | Not reported |
| Alpine | libssh2 | apk | 3.22 | 1.11.1-r2 | Not reported | ALPINE-CVE-2026-55199 | Not reported |
| Alpine | libssh2 | apk | 3.23 | 1.11.1-r3 | Not reported | ALPINE-CVE-2026-55199 | Not reported |
| Alpine | libssh2 | apk | 3.24 | 1.11.1-r3 | Not reported | ALPINE-CVE-2026-55199 | Not reported |
| Alpine | rust | apk | 3.24 | 1.96.1-r0 | Not reported | ALPINE-CVE-2026-55199 | Not reported |
| Ubuntu | libssh2 | deb | 24.04 | 1.11.0-4.1ubuntu0.24.04.2 | Not reported | UBUNTU-CVE-2026-55199 | Not reported |
| Ubuntu | libssh2 | deb | 25.10 | 1.11.1-1ubuntu0.25.10.2 | Not reported | UBUNTU-CVE-2026-55199 | Not reported |
| Ubuntu | libssh2 | deb | 26.04 | 1.11.1-1ubuntu0.26.04.2 | Not reported | UBUNTU-CVE-2026-55199 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise module for basesystem 15 sp7 | 1.11.0-150600.20.3.1 | Not reported | SUSE-SU-2026:3076-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server 15 sp6-ltss | 1.11.0-150600.20.3.1 | Not reported | SUSE-SU-2026:3076-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server for sap applications 15 sp6 | 1.11.0-150600.20.3.1 | Not reported | SUSE-SU-2026:3076-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise high performance computing 15 sp4-espos | 1.11.0-150000.4.32.1 | Not reported | SUSE-SU-2026:3082-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise high performance computing 15 sp4-ltss | 1.11.0-150000.4.32.1 | Not reported | SUSE-SU-2026:3082-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server 15 sp4-ltss | 1.11.0-150000.4.32.1 | Not reported | SUSE-SU-2026:3082-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise micro 5.3 | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise micro 5.4 | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise micro 5.5 | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise high performance computing 15 sp4-espos | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise high performance computing 15 sp4-ltss | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise high performance computing 15 sp5-espos | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise high performance computing 15 sp5-ltss | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server 15 sp4-ltss | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server 15 sp5-ltss | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server for sap applications 15 sp4 | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server for sap applications 15 sp5 | 1.11.0-150200.9.5.1 | Not reported | SUSE-SU-2026:3074-1 | Not reported |
| Suse | libssh2_org | rpm | linux micro 6.0 | 1.11.0-3.1 | Not reported | SUSE-SU-2026:22438-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server 16.0 | 1.11.1-160000.4.1 | Not reported | SUSE-SU-2026:22364-1 | Not reported |
| Suse | libssh2_org | rpm | linux enterprise server for sap applications 16.0 | 1.11.1-160000.4.1 | Not reported | SUSE-SU-2026:22364-1 | Not reported |
| Suse | libssh2_org | rpm | linux micro 6.2 | 1.11.1-160000.4.1 | Not reported | SUSE-SU-2026:22284-1 | Not reported |
| Opensuse | libssh2_org | rpm | leap 16.0 | 1.11.1-160000.4.1 | Not reported | OPENSUSE-SU-2026:21057-1 | Not reported |
OpenFactory catalog packages
[Debian 12 (Bookworm)]
- [libssh2-1]Not affected
Source package: [libssh2]
Details (2)
1.10.0-3+b1· amd64 · bookwormNot affected
nvd · libssh2 · debian · bookworm
1.10.0-3+b1· arm64 · bookwormNot affected
nvd · libssh2 · debian · bookworm
- [libssh2-1-dev]Not affected
Source package: [libssh2]
Details (2)
1.10.0-3+b1· amd64 · bookwormNot affected
nvd · libssh2 · debian · bookworm
1.10.0-3+b1· arm64 · bookwormNot affected
nvd · libssh2 · debian · bookworm
[Debian 13 (Trixie)]
- [libssh2-1-dev]Fixed
Source package: [libssh2]
Details (4)
1.11.1-1+deb13u1· amd64 · trixieFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
1.11.1-1+deb13u1· arm64 · trixieFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
1.11.1-1+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
1.11.1-1+deb13u1· arm64 · trixie-securityFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
- [libssh2-1t64]Fixed
Source package: [libssh2]
Details (4)
1.11.1-1+deb13u1· amd64 · trixieFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
1.11.1-1+deb13u1· arm64 · trixieFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
1.11.1-1+deb13u1· amd64 · trixie-securityFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
1.11.1-1+deb13u1· arm64 · trixie-securityFixed · Fixed:
1.11.1-1+deb13u1nvd · libssh2 · debian · 13
Observed:
References
- [https://ftp.suse.com/pub/projects/security/csaf/suse-su-2026_22284-1.json]
- [https://nvd.nist.gov/vuln/detail/CVE-2026-55199]
- [https://osv.dev/vulnerability/ALPINE-CVE-2026-55199]
- [https://osv.dev/vulnerability/DEBIAN-CVE-2026-55199]
- [https://osv.dev/vulnerability/SUSE-SU-2026:22284-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:22364-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:22438-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:3074-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:3076-1]
- [https://osv.dev/vulnerability/SUSE-SU-2026:3082-1]
- [https://osv.dev/vulnerability/UBUNTU-CVE-2026-55199]
- [https://osv.dev/vulnerability/openSUSE-SU-2026:21057-1]
- [https://security-tracker.debian.org/tracker/CVE-2026-55199]
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-55199.json]
- [https://ubuntu.com/security/notices/USN-8486-1]
- [https://wid.cert-bund.de/.well-known/csaf/white/2026/wid-sec-w-2026-1996.json]
[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [National Vulnerability Database (NVD)] · [OSV Package Vulnerability Database] · [Red Hat security advisories and VEX] · [SUSE security advisories and VEX] · [Ubuntu Security Notices (USN)]