CVE-2026-64375 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
proc: protect ptrace_may_access() with exec_update_lock (FD links)
proc_pid_get_link() and proc_pid_readlink() currently look up the task from the pid once, then do the ptrace access check on that task, then look up the task from the pid a second time to do the actual access. That's racy in several ways.
To fix it, pass the task to the ->proc_get_link() handler, and instead of proc_fd_access_allowed(), introduce a new helper call_proc_get_link() that looks up and locks the task, does the access check, and calls ->proc_get_link().
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Analysis
by VulDB Data Team • 07/25/2026
This vulnerability exists within the Linux kernel's process management subsystem where the proc filesystem implementation contains a race condition in the ptrace access control mechanism. The flaw occurs in the proc_pid_get_link() and proc_pid_readlink() functions which perform redundant task lookups from the pid namespace, creating opportunities for concurrent access violations that could be exploited by malicious processes attempting to manipulate or escalate privileges. The vulnerability specifically affects the interaction between the ptrace subsystem and the proc filesystem when resolving symbolic links for process file descriptors.
The technical implementation flaw stems from the double lookup pattern where the kernel first retrieves a task structure from the pid namespace, performs a ptrace access check against that task, and then performs a second lookup to obtain the same task structure for actual access operations. This creates a window where the task structure could be modified or replaced between the two lookups, allowing an attacker to potentially bypass security checks or access unauthorized process information. The race condition is particularly dangerous because it occurs in kernel space where privilege escalation opportunities can lead to complete system compromise.
The operational impact of this vulnerability extends beyond simple information disclosure to potential privilege escalation scenarios within the Linux kernel. An attacker could exploit this race condition to gain unauthorized access to process memory spaces, manipulate ptrace relationships, or escalate privileges through carefully timed concurrent operations targeting the same pid namespace. The vulnerability affects systems running Linux kernels where the proc filesystem is enabled and ptrace functionality is utilized, potentially impacting server environments, containerized applications, and any system where process monitoring or debugging capabilities are exposed.
Mitigation strategies should focus on implementing proper locking mechanisms around task access operations within the kernel. The recommended fix involves modifying the proc filesystem implementation to pass the task structure directly to the ->proc_get_link() handler instead of performing redundant lookups, while introducing a new helper function call_proc_get_link() that manages the complete sequence of task lookup, locking, and access validation. This approach aligns with common security practices for concurrent access control and addresses the race condition at its root cause. The fix should be implemented following established kernel development practices and security guidelines for preventing race conditions in kernel space operations.
This vulnerability relates to CWE-367 Time-of-Check Time-of-Use error pattern where the state of a resource is checked and then used without proper synchronization, allowing attackers to manipulate the resource between check and use operations. The attack surface covers all systems utilizing ptrace functionality with proc filesystem access, particularly those running multi-threaded applications or containerized environments. From an ATT&CK perspective, this vulnerability maps to privilege escalation techniques and defense evasion methods that leverage kernel-level race conditions to bypass security controls. The fix ensures proper ordering of operations and eliminates the window where concurrent access could be exploited for malicious purposes.