CVE-2026-98614 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
sctp: avoid livelock while updating retransmit path
sctp_assoc_update_retran_path() can loop forever when every remaining transport, including retran_path, is SCTP_UNCONFIRMED: the state check runs before the wraparound test, so the loop cannot observe that it has completed a full pass.
Fix this by considering a transport only when it is not UNCONFIRMED, then checking whether the walk has returned to retran_path. This makes the full-pass termination independent of the transport state while preserving the existing fallback selection semantics.
Also restore the NULL guard around the retran_path assignment. In the all-UNCONFIRMED case there is no eligible replacement transport, and installing NULL would leave later retransmit-path users and the debug print with a NULL path.
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's Stream Control Transmission Protocol (SCTP) implementation contains a critical logic flaw within the sctp_assoc_update_retran_path function that can lead to an infinite loop, commonly referred to as a livelock. This vulnerability arises from the specific order of operations during the transport selection process for retransmitting data. When the system attempts to update the active path for retransmission, it iterates through available network transports to find one suitable for sending packets. The original code structure performs a state check on each transport before verifying whether the iteration has wrapped around and returned to the starting point, known as retran_path. This sequencing error means that if all remaining transports are in an SCTP_UNCONFIRMED state, the loop condition never evaluates to false because it fails to detect the completion of a full pass through the list of available paths. Consequently, the function enters an infinite cycle, consuming CPU resources and potentially causing denial of service for the affected network connection or system processes relying on this kernel routine.
From a technical perspective, this issue is classified under CWE-835, which describes loops that do not terminate correctly due to flawed loop control logic. The root cause lies in the dependency of the termination condition on the state of individual transports rather than on an absolute count or pointer comparison indicating traversal completion. In scenarios where every transport associated with a specific SCTP association is marked as unconfirmed, typically following network failures or peer disconnections, the algorithm fails to break out of its search loop. This behavior not only wastes computational cycles but also prevents other kernel subsystems from making progress, effectively stalling the protocol stack's ability to manage connection state transitions or recover from errors. The vulnerability highlights a subtle but significant defect in how iterative searches over dynamic data structures are bounded within the network layer of the operating system.
The operational impact of this livelock is severe for systems relying on SCTP for reliable, message-oriented communication, such as telecommunication signaling networks and high-availability database clusters. An infinite loop in kernel space can lead to soft lockups where the scheduler cannot preempt the stuck thread if it holds necessary locks or runs with interrupts disabled. This results in a denial of service condition that may require manual intervention or system reboot to resolve. Furthermore, the lack of proper termination means that subsequent operations expecting a valid retransmit path will fail, leading to packet loss and connection instability even after network conditions might have improved. The vulnerability affects the reliability guarantees that SCTP is designed to provide, undermining its utility in mission-critical applications where fault tolerance and automatic failover are essential features.
To mitigate this risk, the fix involves restructuring the loop logic within sctp_assoc_update_retran_path to ensure termination independence from transport states. The updated implementation first checks if a transport is not in an UNCONFIRMED state before considering it for selection. Crucially, it then verifies whether the iteration has returned to the original retran_path pointer, ensuring that a full pass through all available transports has been completed regardless of their individual statuses. This change guarantees loop termination by relying on structural traversal completion rather than conditional state checks alone. Additionally, the patch restores a NULL guard around the assignment of retran_path. In cases where no eligible replacement transport is found because all are unconfirmed, setting the path to NULL prevents later code from dereferencing an invalid pointer or encountering undefined behavior during retransmission attempts and debug logging. This defensive programming approach ensures that the kernel remains stable even when optimal paths are unavailable.
Security researchers and system administrators should monitor for updates to the Linux kernel that include this specific SCTP fix, particularly in environments where SCTP is heavily utilized. The vulnerability aligns with ATT&CK technique T1499, Endpoint Denial of Service, as it allows an attacker or a faulty network condition to exhaust local resources through infinite looping. While typically triggered by network state changes rather than direct malicious input, the potential for resource exhaustion makes this a significant reliability concern. Maintaining up-to-date kernel versions is essential to prevent these logic errors from impacting system availability. The resolution demonstrates the importance of rigorous loop boundary testing in low-level protocol implementations, ensuring that termination conditions are robust against edge cases involving all-unavailable resources.