CVE-2026-98700 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: set info->band for 802.3 encap offload frames
Unlike the 802.11 TX paths, ieee80211_8023_xmit() does not set info->band from the channel context on non-MLD interfaces. It stays at 0, so ieee80211_get_tx_rates() uses the wrong band for these frames.
Set it the same way as ieee80211_build_hdr(): drop the frame if there is no channel context, and leave the band at 0 on MLD interfaces.
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's wireless networking subsystem contains a specific implementation flaw within the mac80211 stack that affects how transmission information is initialized for frames undergoing 802.3 encapsulation offload. This vulnerability arises from an inconsistency in how the band context is assigned to packet metadata compared to standard IEEE 802.11 transmission paths. In typical wireless transmit operations, the driver or mac80211 core ensures that the tx_info structure correctly reflects the operational frequency band and channel parameters before any rate selection logic is invoked. However, in the specific code path handling ieee80211_8023_xmit(), which processes frames destined for offload processing under IEEE 802.3 encapsulation rules on non-Multi-Link Device interfaces, this critical initialization step was omitted. Consequently, the band field within the transmission info structure remains at its default value of zero rather than being populated with the correct channel context derived from the active wireless interface configuration.
This oversight leads to a direct functional defect in rate determination logic during packet transmission. The function ieee80211_get_tx_rates(), which is responsible for selecting appropriate data rates based on current link conditions and hardware capabilities, relies heavily on the band identifier to apply correct modulation schemes and frequency-specific constraints. When this value remains zero due to the missing initialization, the rate selection algorithm operates with incorrect assumptions about the physical layer environment. This mismatch can result in the transmission of frames using inappropriate modulation and coding schemes for the actual operating channel, potentially causing packet loss, reduced throughput, or complete failure of the wireless connection for offloaded traffic streams. The issue is particularly relevant to modern Wi-Fi implementations that support advanced features like 802.3 encapsulation where hardware acceleration handles certain framing tasks but still requires accurate software-side metadata for rate control decisions.
From a security and stability perspective, while this vulnerability primarily manifests as a functional reliability issue rather than a direct exploitation vector for privilege escalation or remote code execution, it represents a significant degradation in service availability and network performance. Incorrect band assignment can lead to intermittent connectivity drops or severe latency spikes, effectively creating a denial of service condition for applications relying on stable wireless connections. The flaw aligns with CWE-20 Improper Input Validation as the system fails to properly validate and initialize internal state variables before use, leading to undefined behavior in subsequent processing stages. Furthermore, it can be mapped to ATT&CK technique T1498 Network Denial of Service if an attacker were able to trigger high volumes of such offloaded traffic, thereby exacerbating the performance degradation caused by incorrect rate selection across multiple clients or interfaces.
The resolution implemented addresses this root cause by enforcing consistent initialization practices across all transmission paths within mac80211. The fix ensures that for non-MLD (Multi-Link Device) interfaces, the band information is explicitly set from the channel context prior to any subsequent processing steps. This mirrors the behavior already established in ieee80211_build_hdr(), thereby standardizing how metadata is prepared regardless of whether a frame follows the traditional 802.11 TX path or the specialized 802.3 encapsulation offload route. For MLD interfaces, where multi-band operations are inherent and complex, the logic retains the band at zero to avoid incorrect assumptions about single-band constraints, acknowledging that these devices operate differently. Additionally, the patch introduces a safeguard that drops frames lacking valid channel context, preventing further propagation of malformed transmission requests through the stack.
To mitigate similar issues in broader system administration or development contexts, it is essential to ensure that all kernel updates are applied promptly, as this fix has been integrated into upstream Linux kernels and subsequent stable releases. System administrators should verify their distribution's patch status for mac80211-related components. For developers working on wireless drivers or custom networking stacks, the key takeaway is the necessity of rigorous state initialization checks before invoking rate control algorithms. Validating that all required metadata fields are populated with accurate context-specific values prevents logical errors in packet processing pipelines. Regular auditing of code paths handling offloaded traffic can help identify similar inconsistencies where hardware acceleration features bypass standard software validation steps, ensuring robust and reliable wireless connectivity across diverse deployment scenarios.