CVE-2026-98251 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
openvswitch: avoid reallocating confirmed conntrack labels
ovs_ct_get_conn_labels() adds the labels extension when a conntrack entry does not have one. Confirmed conntracks can be read locklessly, so adding an extension may reallocate and free the extension block while another CPU accesses it.
Only add the extension for unconfirmed conntracks. A confirmed conntrack without labels now fails the caller's label operation instead of reallocating its extension storage.
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Analysis
by VulDB Data Team • 10/06/2026
The Linux kernel vulnerability identified in Open vSwitch involves a race condition within the connection tracking subsystem, specifically affecting how conntrack labels are managed during packet processing. The core issue resides in the ovs_ct_get_conn_labels function, which is responsible for retrieving or initializing label extensions associated with network connections tracked by the kernel's netfilter framework. When this function encounters a connection track entry that lacks an existing label extension, it attempts to dynamically allocate and attach one on the fly. While this behavior might seem convenient for ensuring data availability, it introduces significant concurrency risks because conntrack entries transition through different states of confirmation during their lifecycle.
The technical flaw stems from the fact that confirmed connection tracks are designed to be accessed locklessly by multiple CPU cores to maximize performance in high-throughput networking scenarios. This optimization allows packets belonging to established flows to bypass expensive locking mechanisms, relying instead on atomic operations and memory barriers for safety. However, the act of adding a new extension involves reallocation of memory blocks associated with that specific conntrack entry. If one CPU core is in the process of reallocating or freeing this extension block while another CPU core is simultaneously reading from it under the assumption of lockless access, a use-after-free condition occurs. This race condition can lead to kernel panics, data corruption, or unpredictable system behavior depending on memory allocation patterns and timing.
From an industry standards perspective, this vulnerability aligns with CWE-416, Use After Free, as well as CWE-362, Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition). The ATT&CK framework categorizes such kernel-level exploitation vectors under techniques that target system stability and availability, potentially enabling denial-of-service attacks. An attacker who can trigger this code path repeatedly may cause the host to crash or become unresponsive, effectively disrupting network services provided by Open vSwitch instances running on affected systems.
The operational impact of this vulnerability is primarily centered around system reliability rather than direct privilege escalation or data exfiltration in most cases. However, consistent triggering could allow a malicious actor with local access or control over specific traffic patterns to induce denial-of-service conditions against the host machine and any virtual networks managed by Open vSwitch. In cloud environments where such kernels are common, this could affect multiple tenants if not properly isolated, leading to broader service disruptions across infrastructure layers.
Mitigation strategies involve applying vendor-provided kernel patches that restrict label extension initialization exclusively to unconfirmed conntrack entries. By ensuring that extensions are only added before the connection enters a confirmed state, the system avoids modifying shared data structures during concurrent read operations. Administrators should ensure their systems are updated with the latest security fixes for Open vSwitch and the Linux kernel. Additionally, monitoring logs for unexpected crashes or oops messages related to netfilter components can help detect potential exploitation attempts in real-time before they cause significant downtime.