The setcred(2) system call is only available to privileged users. However, before the privilege level of the caller is checked, the user-supplied list of supplementary groups is copied into a fixed-size kernel stack buffer without first validating its length. If the supplied list exceeds the capacity of that buffer, a stack buffer overflow occurs. Because the bounds check on the supplementary groups list occurs after the kernel stack buffer has already been written, an unprivileged local user may trigger the overflow without holding any special privilege. Successful exploitation may allow an attacker to execute arbitrary code in the context of the kernel, allowing an unprivileged local user to gain elevated privileges on the affected system.
Casky was already ahead
This CVE exploits attack patterns that Casky's 0matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.
CVE-2026-45250 represents a critical privilege escalation vulnerability in the setcred(2) system call where supplementary group lists are copied into a fixed-size kernel stack buffer without length validation. The vulnerability exists because the privilege check occurs after the unsafe buffer copy, allowing any unprivileged local user to trigger a stack buffer overflow by supplying an oversized group list. This affects any system running vulnerable kernel versions and impacts all local users, making it a high-severity issue (CVSS 7.8) since it enables unprivileged attackers to execute arbitrary code in kernel context and gain full system compromise.
While this CVE maps to CWE-121 (stack-based buffer overflow), it currently lacks specific MITRE ATT&CK technique mappings in public frameworks. Using Casky.ai's Claude-powered analysis with 754 security skills, practitioners would detect attack patterns associated with this vulnerability through behavioral signals: detection of abnormal system call sequences involving setcred with unusually large supplementary group arrays (T1134 - Access Token Manipulation indicators), privilege escalation attempts from unprivileged processes (T1134.003), and post-exploitation patterns showing unexpected kernel-level process execution (T1548 - Abuse Elevation Control Mechanism). Practitioners analyzing kernel logs and system call traces through Casky's extended reasoning capabilities would identify the characteristic overflow signature: legitimate setcred calls preceded by attempts to pass group lists exceeding kernel buffer limits, followed by kernel crash or unexpected privilege transitions—all key indicators of active exploitation of this vulnerability.
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