CVE-2026-60002: 
Rocky Linux vulnerability analysis and mitigation

CVE-2026-60002 is a use-after-free vulnerability in the OpenSSH client (ssh) that can be triggered when a server changes its host key during a key re-exchange operation. The vulnerability affects all versions of OpenSSH before 10.4 and impacts only the client side. It was publicly disclosed on July 8, 2026, following the release of OpenSSH 10.4 on July 6, 2026, which included the fix. The vulnerability was reported by Zhenpeng (Leo) Lin of Depthfirst. CVSS v3.1 scores vary by source: NVD/Feedly assigns 9.4 (Critical), while GitHub Advisory Database and ENISA assign 7.7 (High) with higher attack complexity (GitHub Advisory, Openwall).

The vulnerability is classified as CWE-416 (Use After Free) and CWE-825 (Expired Pointer Dereference). During a post-authentication key re-exchange (rekey), if the server changes its host key, the OpenSSH client can reference memory that has already been freed, leading to a use-after-free condition. The attack vector is network-based and requires no authentication or user interaction, though some scoring sources rate attack complexity as High due to the specific timing and server-side conditions required to trigger the host key change during rekey. The vulnerability was fixed in OpenSSH 10.4, which also introduced stricter transport protocol enforcement by disconnecting if a peer sends non-KEX messages during a post-authentication key re-exchange (Openwall, GitHub Advisory).

Successful exploitation can allow an unauthenticated network attacker (operating as or controlling a malicious SSH server) to read sensitive data from the SSH client's memory and potentially execute arbitrary code with the privileges of the SSH client process. The confidentiality and integrity impacts are rated High, with a Low availability impact. Because the vulnerability is client-side only, the risk is primarily to users connecting to untrusted or compromised SSH servers, where an attacker-controlled server could trigger the condition during a session (GitHub Advisory, Feedly).

As of the time of disclosure, there is no public proof-of-concept exploit and no evidence of in-the-wild exploitation (GitHub Advisory). The NVD SSVC assessment classifies exploitation as "none" and notes the vulnerability is not automatable. The EPSS score is approximately 0.25% (18th percentile), indicating a low near-term exploitation probability. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. No threat actor attribution has been reported (Feedly).

1. Set up a malicious SSH server: An attacker operates or compromises an SSH server that a target client will connect to, or performs a man-in-the-middle position between the client and a legitimate server.
2. Establish an SSH session: Wait for or induce the target SSH client (running OpenSSH < 10.4) to connect to the attacker-controlled server and complete authentication.
3. Initiate key re-exchange: Trigger a key re-exchange (rekey) with the connected client, which is a standard SSH protocol operation that can be initiated by either side.
4. Change host key during rekey: During the key re-exchange process, present a different host key than the one used in the initial handshake, causing the client to process the new key while the old key's memory may be freed.
5. Trigger use-after-free: The client-side SSH code references the freed memory associated with the old host key, resulting in a use-after-free condition that may allow reading of sensitive memory contents or, under favorable conditions, arbitrary code execution in the context of the SSH client process (Openwall, GitHub Advisory).

• Network: SSH connections to unexpected or newly seen server IP addresses; SSH sessions exhibiting unusual key re-exchange patterns or abnormally frequent rekey operations.
• Process: SSH client process (ssh) crashing unexpectedly or producing segmentation faults; unusual child processes spawned from the SSH client after connection establishment.
• Logs: System logs (/var/log/syslog, /var/log/auth.log) showing SSH client crashes or abnormal termination; kernel logs indicating memory corruption or segfault for the ssh process.
• File System: Core dump files generated by the ssh process in the working directory or /var/crash/, which may contain sensitive memory contents including credentials or private key material.

The primary remediation is to upgrade OpenSSH to version 10.4 or later, which contains the fix for this use-after-free vulnerability (Openwall). Distribution-specific patches have been issued for Ubuntu (USN-8533-1), Fedora 43 and 44, and Red Hat/RHEL (Red Hat, Ubuntu Advisory). As a temporary workaround until patching is possible, restrict SSH client connections to only trusted, known-good servers and avoid connecting to untrusted or unknown SSH servers. Network-level controls such as SSH proxies or jump hosts with updated software can also reduce exposure.

The vulnerability was announced as part of the OpenSSH 10.4 release by Damien Miller on the oss-security mailing list, which also detailed several other security fixes in the same release (Openwall). Security news outlets including SecurityOnline.info covered the OpenSSH 10.4 security fixes, and the vulnerability was noted in weekly threat landscape digests. Community discussion on Infosec.Exchange highlighted the release. Red Hat and Ubuntu both issued advisories and updated packages promptly following the disclosure (Red Hat).