RHSA-2024:0455MediumCVSS 6.5

Red Hat Security Advisory: openssh security update

Published
January 25, 2024
Last Modified
August 14, 2026

🔗 CVE IDs covered (2)

CVE-2023-48795 →CVE-2023-51385 →

📋 Description

CVE-2023-48795 — ssh: Prefix truncation attack on Binary Packet Protocol (BPP) CVE-2023-51385 — openssh: potential command injection via shell metacharacters

🎯 Affected products91

  • Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-0:8.7p1-30.el9_2.3.src as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-0:8.7p1-30.el9_2.3.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-askpass-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-0:8.7p1-30.el9_2.3.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-askpass-debuginfo-0:8.7p1-30.el9_2.3.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-0:8.7p1-30.el9_2.3.x86_64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.aarch64 as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.ppc64le as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.s390x as a component of Red Hat Enterprise Linux BaseOS EUS (v.9.2)
  • openssh-clients-debuginfo-0:8.7p1-30.el9_2.3.x86_64 as a component of Red Hat Enterprise Linux AppStream EUS (v.9.2)
  • +61 more not shown

✅ Remediation

For details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258 After installing this update, the OpenSSH server daemon (sshd) will be restarted automatically. Workaround: Update to the last version and check that client and server provide kex pseudo-algorithms indicating usage of the updated version of the protocol which is protected from the attack. If "[email protected]" is provided by clients and "[email protected]" is in the server's reply, no other steps are necessary. Disabling ciphers if necessary: If "[email protected]" is not provided by clients or "[email protected]" is absent in the server's reply, you can disable the following ciphers and HMACs as a workaround on RHEL-8 and RHEL-9: 1. [email protected] 2. [email protected] 3. [email protected] 4. [email protected] 5. [email protected] To do that through crypto-policies, one can apply a subpolicy with the following content: ``` cipher@SSH = -CHACHA20-POLY1305 ssh_etm = 0 ``` e.g., by putting these lines into `/etc/crypto-policies/policies/modules/CVE-2023-48795.pmod`, applying the resulting subpolicy with `update-crypto-policies --set $(update-crypto-policies --show):CVE-2023-48795` and restarting openssh server. One can verify that the changes are in effect by ensuring the ciphers listed above are missing from both `/etc/crypto-policies/back-ends/openssh.config` and `/etc/crypto-policies/back-ends/opensshserver.config`. For more details on using crypto-policies, please refer to https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/9/html/security_hardening/using-the-system-wide-cryptographic-policies_security-hardening Note that this procedure does limit the interoperability of the host and is only suggested as a temporary mitigation until the issue is fully resolved with an update. For RHEL-7: We can recommend to use strict MACs and Ciphers on RHEL7 in both files /etc/ssh/ssh_config and /etc/ssh/sshd_config. Below strict set of Ciphers and MACs can be used as mitigation for RHEL 7. ``` Ciphers aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected] MACs [email protected],[email protected],hmac-sha2-256,hmac-sha2-512 ``` - For Openshift Container Platform 4: Please refer the KCS[1] document for verifying the fix in RHCOS. [1] https://access.redhat.com/solutions/7071748 Workaround: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

🔗 References (5)