Description
A flaw was found in libssh's handling of key exchange (KEX) processes when a client repeatedly sends incorrect KEX guesses. The library fails to free memory during these rekey operations, which can gradually exhaust system memory. This issue can lead to crashes on the client side, particularly when using libgcrypt, which impacts application stability and availability.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| — | libssh | 0.6.0 – < 0.11.3 | 0.11.3 |
| Red Hat | Red Hat Enterprise Linux 9 | — | — |
| Red Hat | Red Hat Enterprise Linux 10 | — | — |
| Red Hat | Red Hat Enterprise Linux 6 | — | — |
| Red Hat | Red Hat Enterprise Linux 7 | — | — |
| Red Hat | Red Hat Enterprise Linux 8 | — | — |
| Red Hat | Red Hat OpenShift Container Platform 4 | — | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | libssh | 0.11.3-1 | — |
| Debian 13 | libssh | 0.11.2-1+deb13u1 | — |
| Debian 12 | libssh | 0.10.6-0+deb12u2 | — |
| Debian 11 | libssh | 0.9.8-0+deb11u2 | DLA-4385-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 25.10 | libssh | 0.11.2-1ubuntu0.2 | USN-8051-1 |
| Ubuntu 24.04 LTS | libssh | 0.10.6-2ubuntu0.3 | USN-8051-1 |
| Ubuntu 22.04 LTS | libssh | 0.9.6-2ubuntu0.22.04.6 | USN-8051-1 |
Show 2 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 20.04 LTS | libssh | 0.9.3-2ubuntu2.5+esm3 | — |
| Ubuntu Pro 18.04 LTS | libssh | 0.8.0~20170825.94fa1e38-1ubuntu0.7+esm6 | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 9 | libssh +2 | 0.10.4-18.el9 | RHSA-2026:18683 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 9 | libssh +2 | 0.10.4-18.el9 | ALSA-2026:18683 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 9 | libssh | 0.10.4-18.el9 | RLSA-2026:18683 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | libssh | 0.9.8-150600.11.6.1 | SUSE-SU-2025:03369-1 |
| SLES 15 SP6 | libssh | 0.9.8-150600.11.6.1 | SUSE-SU-2025:03369-1 |
| SLES 12 SP5 | libssh | 0.6.3-12.18.1 | SUSE-SU-2025:3897-1, SUSE-SU-2025:03368-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLE Micro 6.1 | libssh | 0.10.6-slfo.1.1_3.1 | SUSE-SU-2025:20894-1 |
| SLE Micro 6.0 | libssh | 0.10.6-3.1 | SUSE-SU-2025:20847-1 |
| SLE Micro 5.5 | libssh | 0.9.8-150400.3.12.1 | SUSE-SU-2025:3788-1 |
| SLE Micro 5.4 | libssh | 0.9.8-150400.3.12.1 | SUSE-SU-2025:3788-1 |
| SLE Micro 5.3 | libssh | 0.9.8-150400.3.12.1 | SUSE-SU-2025:3788-1 |
| SLE Micro 5.2 | libssh | 0.9.8-150200.13.12.1 | SUSE-SU-2025:3787-1 |
| SLE Micro 5.1 | libssh | 0.9.8-150200.13.12.1 | SUSE-SU-2025:3787-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | libssh | 0.11.3-1.1 | openSUSE-SU-2025:15545-1 |
| openSUSE Leap 15.6 | libssh | 0.9.8-150600.11.6.1 | SUSE-SU-2025:03369-1 |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | libssh +2 | 0.10.6-1.amzn2023.0.3 | ALAS2023-2025-1264 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | libssh | 0.10.6-4 | — |
| Azure Linux 2 (CBL-Mariner) | libssh | 0.10.6-5 | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 9 | libssh +2 | 0.10.4-18.el9 | ELSA-2026-18683 |
Advisories 16
- ALSA-2026:18683 Moderate: libssh security update AlmaLinux Security Advisories · Oct 29, 2026
- RHSA-2026:18683 Red Hat Security Advisory: libssh security update Red Hat Security Advisories (RHSA) · Oct 17, 2026
- WID-SEC-2025-2002 libssh: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Oct 4, 2026
- ELSA-2026-18683 Moderate: libssh security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Jun 12, 2026
- RLSA-2026:18683 Moderate: libssh security update Rocky Linux Security Advisories · May 28, 2026
- USN-8051-1 libssh vulnerabilities Ubuntu Security Notices (USN) · May 14, 2026
- openSUSE-SU-2025:15545-1 libssh-config-0.11.3-1.1 on GA media SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20894-1 Security update for libssh SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:20847-1 Security update for libssh SUSE / openSUSE Security Updates · Mar 23, 2026
- SUSE-SU-2025:03369-1 Security update for libssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:3788-1 Security update for libssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:3787-1 Security update for libssh SUSE / openSUSE Security Updates · Feb 4, 2026
- SUSE-SU-2025:3897-1 Security update for libssh SUSE / openSUSE Security Updates · Feb 4, 2026
- DLA-4385-1 libssh - security update Debian Security (DSA / DLA) · Nov 27, 2025
- ALAS2023-2025-1264 Moderate: libssh security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Nov 10, 2025
- SUSE-SU-2025:03368-1 Security update for libssh SUSE / openSUSE Security Updates · Sep 26, 2025
References
- RHSA-2026:18683 vendor-advisory
- https://access.redhat.com/security/cve/CVE-2025-8277 vdb-entry
- RHBZ#2383888 issue-tracking
- https://www.libssh.org/security/advisories/CVE-2025-8277.txt