CVE-2026-74490 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
tipc: avoid use-after-free in poll trace queue dumps
TIPC socket tracepoints dump queue state through tipc_sk_dump(). Most queue-dump callsites already serialize that walk under the socket lock or sk->sk_lock.slock, but tipc_poll() calls trace_tipc_sk_poll(..., TIPC_DUMP_ALL, ...) without holding either lock.
That lets the poll trace path reach tipc_list_dump() and backlog head/tail dumping while another context dequeues and frees an skb, leaving the trace helper dereferencing a stale queue entry.
Stop the unlocked poll trace site from requesting queue dumps. Other queue dump trace callsites keep their existing output under the locking they already provide, while poll still emits the event itself without walking live queue members from an unlocked context.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability in question affects the Linux kernel's TIPC (Transparent Inter-Process Communication) subsystem and represents a classic use-after-free condition that can lead to system instability and potential security implications. This issue specifically manifests in the poll trace functionality where the tipc_poll() function invokes trace_tipc_sk_poll() with the TIPC_DUMP_ALL parameter without acquiring proper locking mechanisms. The fundamental problem arises from the lack of synchronization between the tracepoint execution context and the underlying socket queue operations, creating a race condition scenario that allows for memory corruption during concurrent access patterns.
The technical flaw occurs when tipc_poll() function attempts to dump queue state through the tipc_sk_dump() helper without holding either the socket lock or the sk->sk_lock.slock. This unguarded access pattern enables the trace path to reach tipc_list_dump() and perform backlog head/tail dumping operations while another execution context is simultaneously dequeuing and freeing socket buffer packets. The resulting race condition causes the trace helper to dereference stale queue entries that have already been freed, leading to use-after-free conditions that can manifest as kernel crashes, memory corruption, or potentially exploitable memory access violations.
From an operational perspective, this vulnerability presents significant risks to system stability and security within Linux environments that utilize TIPC networking protocols. The race condition can occur during high-concurrency scenarios where multiple processes interact with TIPC sockets simultaneously, making the vulnerability particularly dangerous in production systems where network traffic patterns are unpredictable. The impact extends beyond simple service disruption since kernel memory corruption can potentially allow privilege escalation or denial of service attacks, especially when combined with other exploitation techniques. This type of vulnerability aligns with CWE-416 which specifically addresses use-after-free errors in memory management.
The mitigation strategy implemented in the fix involves modifying the unlocked poll trace site to avoid requesting queue dumps entirely while maintaining the core functionality of emitting poll events. This approach ensures that the poll trace event itself continues to function correctly without attempting to walk live queue members from an unlocked context, thus preventing the race condition that leads to memory corruption. The solution maintains existing locking mechanisms for other queue dump trace callsites, ensuring that they continue to provide their full output under proper synchronization while isolating the problematic access pattern in the poll function itself. This defensive programming approach aligns with ATT&CK technique T1068 which involves exploiting local system privileges and represents a common pattern in kernel security hardening where race conditions are eliminated through proper locking mechanisms.
The fix demonstrates proper adherence to kernel security best practices by addressing the root cause rather than merely patching symptoms. The solution prevents the specific scenario that leads to use-after-free conditions while preserving functional integrity of the TIPC subsystem. This approach follows the principle of least privilege in kernel space operations and ensures that tracepoint functionality does not compromise system stability through unsafe memory access patterns. The vulnerability highlights the importance of careful synchronization in kernel networking code where multiple execution contexts may simultaneously access shared data structures, making it a critical consideration for other kernel subsystems that implement similar tracepoint mechanisms with queue introspection capabilities.