CVE-2026-98823 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: cfg80211: preserve hidden-group beacon IE ownership
A hidden-group probe-response entry borrows its beacon IEs from the group's beacon entry. cfg80211_update_assoc_bss_entry() can pass such an entry to cfg80211_update_known_bss() when merging scan entries after a channel switch.
Copying the borrowed beacon_ies into the associated entry gives the same allocation two owners. Releasing the group's beacon entry can then leave the associated entry pointing to freed IEs, which are freed again when that entry is released.
Skip beacon IE replacement when the source entry belongs to a hidden group. Preserve probe-response processing, the subsequent metadata updates, and the existing rejection path for conflicting hidden beacon updates.
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Analysis
by VulDB Data Team • 10/18/2026
The vulnerability identified in the Linux kernel's wireless subsystem involves a use-after-free condition within the cfg80211 module, specifically concerning the handling of Beacon Information Elements (IEs) during channel switch operations. This issue arises from an incorrect ownership model for data structures associated with hidden groups in Wi-Fi networks. In such configurations, probe-response entries are designed to borrow their beacon IEs directly from a parent group's beacon entry rather than maintaining independent copies. While this borrowing mechanism is efficient for memory usage and consistency during normal operation, it creates a critical dependency that the kernel's association update logic fails to respect properly.
The technical flaw occurs within the cfg80211_update_assoc_bss_entry function, which is responsible for merging scan entries after a channel switch event. When this function processes an entry belonging to a hidden group, it incorrectly proceeds to copy the borrowed beacon IEs into the newly associated BSS (Basic Service Set) entry. This action effectively creates two distinct pointers referencing the same memory allocation: one held by the original group's beacon structure and another by the new association entry. Consequently, the system loses track of which component is responsible for managing the lifecycle of that specific memory block, violating fundamental principles of resource ownership in kernel programming.
The operational impact manifests when the original group's beacon entry is released or deallocated as part of standard cleanup procedures. Because the associated entry still holds a pointer to this now-freed memory region, it becomes a dangling reference. If the system subsequently attempts to access these IEs through the association entry, it results in undefined behavior, potentially leading to kernel panics, data corruption, or arbitrary code execution if an attacker can influence the allocation patterns that overwrite the freed memory. Furthermore, when the associated entry is eventually released, it may attempt to free the same memory block a second time, triggering a double-free vulnerability which further destabilizes the system and exacerbates security risks by allowing potential exploitation of heap metadata corruption.
This flaw aligns with CWE-416, Use After Free, as well as CWE-415, Double Free, depending on the specific execution path taken during memory deallocation. From a threat modeling perspective using MITRE ATT&CK techniques, this vulnerability could be leveraged for privilege escalation or denial of service by triggering kernel crashes through crafted wireless frames that induce channel switches and subsequent association updates in hidden group scenarios. The lack of proper boundary checks regarding data ownership allows an attacker to manipulate the state of network interfaces remotely if they can inject specific probe responses or influence scan results, although exploitation typically requires proximity to the target device's Wi-Fi interface.
To mitigate this vulnerability, developers must enforce strict separation of concerns between borrowed and owned resources within the cfg80211 subsystem. The primary fix involves modifying the beacon IE replacement logic to detect when a source entry belongs to a hidden group and skipping the copying process in such cases. By preserving probe-response processing while avoiding the duplication of borrowed pointers, the kernel ensures that only one entity owns each memory allocation at any given time. This approach maintains metadata updates and existing rejection paths for conflicting hidden beacon updates without introducing dual ownership. System administrators should apply available kernel patches immediately to resolve this issue, ensuring that wireless drivers operate with correct memory management practices that prevent dangling references and double-free conditions in high-throughput or complex network environments involving hidden SSIDs and channel switches.