RHSA-2026:62217 - Security Advisory

Topic

An update for libssh is now available for Red Hat Enterprise Linux 9.

Red Hat Product Security has rated this update as having a security impact of Moderate. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

libssh is a library which implements the SSH protocol. It can be used to implement client and server applications.

Security Fix(es):

• libssh: libssh: denial of service via zero advertised channel packet size (CVE-2026-59843)
• libssh: libssh: denial of service via oversized SFTP read length (CVE-2026-59844)
• libssh: libssh: denial of service via unchecked ProxyCommand fork() failure (CVE-2026-59845)
• libssh: libssh: information disclosure via ProxyCommand %r username expansion (CVE-2026-59846)
• libssh: libssh: integrity downgrade via OpenSSL AES-GCM tag verification (CVE-2026-59847)
• libssh: libssh: denial of service via SFTP responses with unknown request IDs (CVE-2026-59848)
• libssh: libssh: use-after-free via data callbacks on closed channels (CVE-2026-59850)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

Affected Products

• Red Hat Enterprise Linux for x86_64 9 x86_64
• Red Hat Enterprise Linux for x86_64 - Extended Update Support 9.8 x86_64
• Red Hat Enterprise Linux for IBM z Systems 9 s390x
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 9.8 s390x
• Red Hat Enterprise Linux for Power, little endian 9 ppc64le
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 9.8 ppc64le
• Red Hat Enterprise Linux for ARM 64 9 aarch64
• Red Hat Enterprise Linux for ARM 64 - Extended Update Support 9.8 aarch64
• Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions 9.8 ppc64le
• Red Hat Enterprise Linux for x86_64 - Update Services for SAP Solutions 9.8 x86_64
• Red Hat Enterprise Linux for ARM 64 - 4 years of updates 9.8 aarch64
• Red Hat Enterprise Linux for IBM z Systems - 4 years of updates 9.8 s390x
• Red Hat Enterprise Linux for x86_64 - Extended Life Cycle 9.8 x86_64
• Red Hat Enterprise Linux for ARM 64 - Extended Life Cycle 9.8 aarch64
• Red Hat Enterprise Linux for Power, little endian - Extended Life Cycle 9.8 ppc64le
• Red Hat Enterprise Linux for IBM z Systems - Extended Life Cycle 9.8 s390x

Fixes

• BZ - 2498176 - CVE-2026-59843 libssh: libssh: denial of service via zero advertised channel packet size
• BZ - 2498177 - CVE-2026-59844 libssh: libssh: denial of service via oversized SFTP read length
• BZ - 2498178 - CVE-2026-59845 libssh: libssh: denial of service via unchecked ProxyCommand fork() failure
• BZ - 2498179 - CVE-2026-59846 libssh: libssh: information disclosure via ProxyCommand %r username expansion
• BZ - 2498180 - CVE-2026-59847 libssh: libssh: integrity downgrade via OpenSSL AES-GCM tag verification
• BZ - 2498181 - CVE-2026-59848 libssh: libssh: denial of service via SFTP responses with unknown request IDs
• BZ - 2498183 - CVE-2026-59850 libssh: libssh: use-after-free via data callbacks on closed channels

CVEs

• CVE-2026-59843
• CVE-2026-59844
• CVE-2026-59845
• CVE-2026-59846
• CVE-2026-59847
• CVE-2026-59848
• CVE-2026-59850

References

• https://access.redhat.com/security/updates/classification/#moderate