Description

The implementation of this ioctl attempts to acquire locks on all channels in a sync group. If locking a channel would block, it releases the sync group list lock and sleeps. Upon reawakening, it is possible that the sync group structure is freed, but the implementation did not handle this possibility. On a system with a multiple audio devices, an unprivileged local user can exploit this use-after-free to escalate privileges.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.8",
  "pubDate": "2026-08-26T05:18:12.337Z",
  "pubdate": "2026-08-26T05:18:12.337Z",
  "executiveSummary": "A critical use-after-free vulnerability exists in the ioctl implementation responsible for managing sync groups across audio devices. The vulnerability arises from an improper synchronization pattern where the internal state of a sync group structure is not validated after a thread blocks and subsequently reawakens.\nThis flaw allows an unprivileged local attacker to trigger a race condition that results in the use of a freed kernel memory object. If successfully exploited, this can lead to arbitrary code execution within the kernel context, resulting in privilege escalation and full system compromise.\nThe vulnerability is localized to systems managing multiple audio devices and requires local access to the system. No specific authentication beyond standard user access is required, as the ioctl interface is typically exposed to unprivileged processes. Given the nature of use-after-free vulnerabilities in kernel space, this poses a high risk to system integrity and data confidentiality.",
  "technicalDetails": "The root cause of this vulnerability is a race condition within the kernel-level ioctl handler responsible for multi-channel synchronization. When an ioctl request is issued to acquire locks for all channels associated with a specific sync group, the handler attempts to lock individual channel structures sequentially. During this acquisition process, if a lock cannot be obtained immediately, the thread releases the global sync group list lock and enters a sleep state to wait for resource availability.\nThe flaw manifests because the kernel fails to perform a re-validation or reference count check on the sync group structure upon reawakening. In a multi-threaded audio environment, another thread may have deallocated or freed the sync group memory while the first thread was blocked. When the thread resumes execution, it continues to operate on the stale pointer reference, leading to a classic use-after-free condition. Because the sync group structure is no longer valid, subsequent operations—such as dereferencing pointers within the structure or updating list metadata—occur on memory that may have been repurposed or unmapped.\nAn attacker can exploit this by forcing the system to allocate and rapidly free sync group objects while concurrently triggering the locking ioctl. By carefully timing the contention on the audio device locks, the attacker increases the probability that the target structure is freed during the brief window while the thread is in a sleep state. After reawakening, the thread interacts with the freed memory; if the attacker has successfully performed heap grooming (e.g., via spraying the kernel heap with controlled data), they can influence the contents of the freed memory. This allows an attacker to gain control over function pointers or critical data members within the sync group structure.\nThe post-exploitation impact includes the ability to redirect execution flow, bypass kernel security features, or escalate privileges from an unprivileged local user to root. The vulnerability effectively turns a race condition into a memory corruption primitive, allowing for arbitrary read/write access to kernel memory space. As this occurs within the audio subsystem's kernel driver code, the vulnerability is reachable by any process capable of opening the audio device file descriptors."
}