CVE-2026-64111 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
lsm: hold cred_guard_mutex for lsm_set_self_attr()
Just as proc_pid_attr_write() already does before calling the LSM hook. This only matters for SELinux and AppArmor which check whether the process is being ptraced and if so, whether to allow the transition.
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Analysis
by VulDB Data Team • 07/20/2026
The vulnerability addressed in this Linux kernel patch relates to improper synchronization within the Linux Security Module framework, specifically concerning credential management during security attribute transitions. The issue stems from insufficient mutex protection when executing LSM (Linux Security Module) hooks that govern process security attributes. This flaw affects the core security infrastructure by potentially allowing unauthorized privilege escalation or bypass of security controls during critical system operations.
The technical implementation defect occurs within the lsm_set_self_attr() function which fails to acquire the cred_guard_mutex lock before invoking LSM hooks, unlike the proc_pid_attr_write() function that properly implements this protection. This mutex serves as a critical synchronization primitive that ensures atomicity when modifying process credentials and security attributes. The vulnerability becomes particularly significant for SELinux and AppArmor implementations which perform detailed checks on ptrace operations to determine if security transitions should be permitted.
The operational impact of this vulnerability extends beyond simple privilege escalation scenarios to encompass potential bypass of mandatory access controls that rely on ptrace checking mechanisms. When a process attempts to modify its own security attributes through LSM hooks, the absence of proper mutex protection creates a race condition where concurrent operations could interfere with security decisions. This scenario particularly affects systems using SELinux or AppArmor where ptrace permissions directly influence whether security transitions are allowed, potentially enabling malicious processes to circumvent established security policies.
Security implications of this flaw align with CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization) and relate to ATT&CK technique T1068 (Local Privilege Escalation) through potential exploitation pathways. The vulnerability represents a race condition in credential management that could be exploited by processes attempting to manipulate their own security context while under ptrace monitoring. Mitigation strategies should focus on ensuring proper mutex acquisition in all LSM hook execution paths, particularly those involving credential modifications and security attribute transitions. System administrators should prioritize kernel updates that implement this mutex protection, as the vulnerability creates potential attack vectors for bypassing mandatory access controls in environments relying on SELinux or AppArmor security modules.
The fix demonstrates the importance of consistent synchronization patterns throughout kernel security subsystems, where all functions modifying shared security state must acquire appropriate locks before executing LSM hooks. This patch reinforces fundamental security principles by ensuring that credential modifications maintain atomicity and integrity, preventing potential exploitation scenarios that could undermine the entire security framework. The implementation emphasizes the critical nature of proper mutex usage in kernel space operations where concurrent access to sensitive security data could lead to unauthorized privilege escalation or policy bypass situations.