A flaw was found in libssh when using the ChaCha20 cipher with the OpenSSL library. If an attacker manages to exhaust the heap space, this error is not detected and may lead to libssh using a partially initialized cipher context. This occurs because the OpenSSL error code returned aliases with the SSH_OK code, resulting in libssh not properly detecting the error returned by the OpenSSL library. This issue can lead to undefined behavior, including compromised data confidentiality and integrity or crashes.
https://bugzilla.redhat.com/show_bug.cgi?id=2376219
https://access.redhat.com/security/cve/CVE-2025-5987
https://access.redhat.com/errata/RHSA-2026:0978
https://access.redhat.com/errata/RHSA-2026:0702
https://access.redhat.com/errata/RHSA-2026:0431
https://access.redhat.com/errata/RHSA-2026:0430
https://access.redhat.com/errata/RHSA-2026:0428
https://access.redhat.com/errata/RHSA-2026:0427