CVE-2026-3497 in OpenSSH
Summary
by MITRE • 03/12/2026
Vulnerability in the OpenSSH GSSAPI delta included in various Linux distributions. This vulnerability affects the GSSAPI patches added by various Linux distributions and does not affect the OpenSSH upstream project itself. The usage of sshpkt_disconnect() on an error, which does not terminate the process, allows an attacker to send an unexpected GSSAPI message type during the GSSAPI key exchange to the server, which will call the underlying function and continue the execution of the program without setting the related connection variables. As the variables are not initialized to NULL the code later accesses those uninitialized variables, accessing random memory, which could lead to undefined behavior. The recommended workaround is to use ssh_packet_disconnect() instead, which does terminate the process. The impact of the vulnerability depends heavily on the compiler flag hardening configuration.
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Analysis
by VulDB Data Team • 06/03/2026
The vulnerability described in CVE-2026-3497 represents a critical security flaw within the OpenSSH GSSAPI implementation that has been introduced through distribution-specific patches rather than existing in the official OpenSSH source code. This issue specifically targets the GSSAPI key exchange process where Linux distributions have incorporated additional patches that create a dangerous execution path when error conditions occur. The vulnerability stems from the improper handling of error states during GSSAPI communication, where the sshpkt_disconnect() function is invoked but fails to terminate the process completely, leaving the program in an inconsistent state. This flaw falls under the category of improper error handling and memory management issues, aligning with CWE-704 and CWE-476 classifications that address incorrect handling of error conditions and use of uninitialized variables respectively.
The technical execution of this vulnerability occurs during the GSSAPI key exchange phase when an attacker can manipulate the communication flow by sending unexpected GSSAPI message types to the server. When the server encounters these malformed messages, the sshpkt_disconnect() function is called but does not properly terminate the process, allowing execution to continue through the program's code path. This continuation leads to the use of uninitialized connection variables that were never properly set to NULL values during the error handling sequence. The uninitialized variables contain random memory values that are subsequently accessed by the program logic, creating a scenario where arbitrary memory locations are dereferenced, leading to unpredictable behavior that could manifest as crashes, data corruption, or potentially exploitable conditions. This type of vulnerability is particularly dangerous because it operates within the core authentication mechanism of SSH connections, providing attackers with potential pathways for privilege escalation or denial of service attacks.
The operational impact of CVE-2026-3497 extends beyond simple service disruption to potentially enable more sophisticated attacks depending on the system configuration and compiler hardening settings. The vulnerability's effectiveness is directly correlated with the compiler flags used during compilation, particularly those related to memory protection and stack canaries. Systems with weaker hardening configurations may be more susceptible to exploitation, while those with robust compiler protections might mitigate some of the potential attack vectors. The flaw's presence in distribution-specific patches means that organizations running patched versions of OpenSSH from vendors like Red Hat, Ubuntu, or Debian may still be vulnerable if they have applied these particular GSSAPI modifications. This creates a complex landscape where security teams must carefully audit their system configurations and verify that the specific patches applied to their OpenSSH installations do not introduce this vulnerability, as the upstream OpenSSH project itself remains unaffected by this particular issue.
The recommended mitigation strategy involves implementing a direct replacement of sshpkt_disconnect() with ssh_packet_disconnect() throughout the affected code paths, as the latter function properly terminates the process execution when invoked. This change ensures that error conditions during GSSAPI key exchange result in immediate process termination rather than allowing execution to continue in an undefined state. Security administrators should prioritize updating their distribution packages to versions that contain the corrected implementation, while also implementing monitoring systems to detect unusual GSSAPI message patterns that might indicate exploitation attempts. Organizations should also consider disabling GSSAPI authentication temporarily if they cannot immediately apply the patch, particularly in environments where the risk of exploitation is high. This vulnerability demonstrates the importance of thorough code review and testing of distribution-specific patches, as modifications to core security functions can introduce subtle but dangerous flaws that may not be immediately apparent during initial deployment phases. The ATT&CK framework classification for this vulnerability would likely fall under T1078 for valid accounts and T1210 for exploitation of remote services, as it targets the authentication mechanism of SSH services and could potentially be leveraged for unauthorized access or system compromise.