CVE-2026-98708 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: keep paired old chanctx alive
An in-place replacement keeps reciprocal replace_ctx pointers between the old WILL_BE_REPLACED chanctx and the new REPLACES_OTHER chanctx. However, the early free paths only consider assigned and reserved link users when deciding whether to free the old chanctx.
That lets the old chanctx be freed too early while the replacement partner still points back to it, either when the last assigned link is released or when that link successfully reassigns to another existing context. Later unreserve and switch-finalization paths can then follow a stale replace_ctx pointer.
Keep a paired old chanctx alive until the replacement pair has been torn down. Apply the same check to both __ieee80211_link_release_channel() and ieee80211_link_use_reserved_reassign(). If the replacement is later abandoned, ieee80211_link_unreserve_chanctx() already tears down the pairing before freeing the old chanctx once no users remain.
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Analysis
by VulDB Data Team • 10/19/2026
The vulnerability identified in the Linux kernel within the mac80211 wireless subsystem involves a use-after-free condition related to channel context management during dynamic frequency selection and link reconfiguration operations. The core technical flaw lies in the lifecycle management of channel contexts, specifically when an old channel context is being replaced by a new one through an in-place replacement mechanism. This process establishes reciprocal pointers between the old context, marked as WILL_BE_REPLACED, and the new context, which acts as REPLACES_OTHER. While this pointer structure facilitates coordination during the transition, the kernel's early free paths incorrectly determine when it is safe to deallocate memory for the old channel context. These logic paths only account for assigned and reserved link users, failing to consider that a replacement partner may still hold an active reference or dependency on the old context via its reciprocal replace_ctx pointer.
This oversight allows the operating system to prematurely free the memory associated with the old channel context while the new context retains a dangling pointer back to it. This situation arises either when the last assigned link is released from the old context or when that link successfully reassigns itself to another existing context, thereby removing its direct association with the old entity but leaving the structural dependency intact. Consequently, subsequent operations such as unreserve procedures and switch-finalization routines may attempt to dereference this stale pointer. Dereferencing a freed memory address constitutes a classic use-after-free vulnerability, which can lead to unpredictable system behavior, including kernel panics, data corruption, or potential privilege escalation if an attacker can manipulate the state of these pointers through crafted wireless frames that trigger rapid channel context changes.
From a security taxonomy perspective, this flaw aligns with CWE-416, Use After Free, as it involves accessing memory after it has been returned to the system allocator without proper validation of active references. In terms of attack vectors and techniques, this vulnerability relates to ATT&CK technique T1203, Exploitation for Defense Evasion or Privilege Escalation, specifically through exploitation of software vulnerabilities in kernel components. The impact on operational integrity is significant because mac80211 handles critical wireless connectivity functions; a crash here can result in denial of service by disabling network interfaces entirely. Furthermore, if the memory reuse patterns allow an attacker to control data written into the freed region before it is reallocated, there may be opportunities for arbitrary code execution within kernel space, compromising the entire host system's security posture.
To mitigate this vulnerability and prevent premature deallocation, developers have implemented a logic change that ensures the paired old channel context remains alive until the replacement pair has been fully torn down. This fix applies consistent checks to both __ieee80211_link_release_channel() and ieee80211_link_use_reserved_reassign(), ensuring that reference counting accurately reflects all dependencies, including those from replacement partners. Additionally, if a planned channel context replacement is abandoned before completion, the function ieee80211_link_unreserve_chanctx() now correctly tears down the pairing relationship before freeing the old channel context once no other users remain. This adjustment ensures that memory safety rules are strictly enforced during dynamic wireless configuration changes, eliminating the window of opportunity for exploitation via stale pointer dereferences and restoring robustness to the kernel's wireless stack under high-frequency reconfiguration scenarios.