CVE-2025-8277

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.

The Red Hat Product Security team has assessed the severity of this vulnerability as Low.The issue requires an authenticated client to repeatedly initiate key exchanges with incorrect guesses, which leads to memory not being properly released. While this flaw can result in gradual memory exhaustion and potential denial of service (DoS) on the client side, it is not easily exploitable in typical usage scenarios and does not affect servers. The vulnerability does not compromise confidentiality or integrity and poses limited impact on system availability under normal operating conditions.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. It is strongly advised to apply updated libssh packages once available to prevent memory exhaustion risks on client systems.