RHSA-2026:99592 - Security Advisory

Topic

An update for openssh is now available for Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support and Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On.

Red Hat Product Security has rated this update as having a security impact of Important. 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

OpenSSH is an SSH protocol implementation supported by a number of Linux, UNIX, and similar operating systems. It includes the core files necessary for both the OpenSSH client and server.

Security Fix(es):

• openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Red Hat Enterprise Linux OpenSSH client versions (CVE-2026-55655)
• openssh: Double free in Red Hat Enterprise Linux versions of OpenSSH DH-GEX client path during FIPS known-group validation leads to client-side denial of service (CVE-2026-55653)
• openssh: OpenSSH: sftp client allows attacker to control downloaded file location (CVE-2026-59995)
• openssh: OpenSSH sshd: Security bypass due to incorrect handling of forwarding and tunneling options (CVE-2026-59999)
• openssh: openssh: Information disclosure via shared compression side-channel (CVE-2026-106582)
• openssh: OpenSSH: Credential disclosure via failed GSSAPI authentication (CVE-2026-106553)
• openssh: openssh: Denial of service via oversized decompressed packets (CVE-2026-106585)
• openssh: openssh: Command injection via unvalidated command-line username (CVE-2026-106583)

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 - Extended Life Cycle Long Life 8.6 x86_64
• Red Hat Enterprise Linux Server - AUS 8.6 x86_64

Fixes

• BZ - 2462250 - CVE-2026-55655 openssh: Local MITM of X11 forwarding via abstract UNIX socket pre-binding in Red Hat Enterprise Linux OpenSSH client versions
• BZ - 2462351 - CVE-2026-55653 openssh: Double free in Red Hat Enterprise Linux versions of OpenSSH DH-GEX client path during FIPS known-group validation leads to client-side denial of service
• BZ - 2497927 - CVE-2026-59995 openssh: OpenSSH: sftp client allows attacker to control downloaded file location
• BZ - 2497942 - CVE-2026-59999 openssh: OpenSSH sshd: Security bypass due to incorrect handling of forwarding and tunneling options
• BZ - 2547181 - CVE-2026-106582 openssh: openssh: Information disclosure via shared compression side-channel
• BZ - 2547191 - CVE-2026-106553 openssh: OpenSSH: Credential disclosure via failed GSSAPI authentication
• BZ - 2547200 - CVE-2026-106585 openssh: openssh: Denial of service via oversized decompressed packets
• BZ - 2547243 - CVE-2026-106583 openssh: openssh: Command injection via unvalidated command-line username

CVEs

• CVE-2026-55653
• CVE-2026-55655
• CVE-2026-59995
• CVE-2026-59999
• CVE-2026-106553
• CVE-2026-106582
• CVE-2026-106583
• CVE-2026-106585

References

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