CVE-2026-31394
Analyzed Analyzed - Analysis Complete
Null Pointer Dereference in Linux mac80211 AP_VLAN Handling

Publication date: 2026-04-03

Last updated on: 2026-05-20

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations ieee80211_chan_bw_change() iterates all stations and accesses link->reserved.oper via sta->sdata->link[link_id]. For stations on AP_VLAN interfaces (e.g. 4addr WDS clients), sta->sdata points to the VLAN sdata, whose link never participates in chanctx reservations. This leaves link->reserved.oper zero-initialized with chan == NULL, causing a NULL pointer dereference in __ieee80211_sta_cap_rx_bw() when accessing chandef->chan->band during CSA. Resolve the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data. [also change sta->sdata in ARRAY_SIZE even if it doesn't matter]
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Meta Information
Published
2026-04-03
Last Modified
2026-05-20
Generated
2026-06-16
AI Q&A
2026-04-04
EPSS Evaluated
2026-06-14
NVD
CVE-2026-31394
EUVD
EUVD-2026-18770
Affected Vendors & Products
Showing 7 associated CPEs
Vendor Product Version / Range
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel From 6.13 (inc) to 6.18.20 (exc)
linux linux_kernel From 6.19 (inc) to 6.19.10 (exc)
linux linux_kernel From 6.11 (inc) to 6.12.78 (exc)
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-476 The product dereferences a pointer that it expects to be valid but is NULL.
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Mitigation Strategies

The vulnerability is resolved by updating the Linux kernel to a version that includes the fix for the mac80211 crash in ieee80211_chan_bw_change for AP_VLAN stations.

Specifically, the fix involves resolving the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data, preventing the NULL pointer dereference.

Therefore, the immediate mitigation step is to apply the kernel update or patch that contains this fix.

Executive Summary

This vulnerability exists in the Linux kernel's mac80211 component, specifically in the ieee80211_chan_bw_change function. The function iterates over all stations and accesses certain link data via station structures. For stations on AP_VLAN interfaces, the link data is zero-initialized and does not participate in channel context reservations, leading to a NULL pointer dereference when the code tries to access channel information during a channel switch announcement (CSA). This causes a crash. The fix involves resolving the VLAN station data to its parent access point station data before accessing the link data, preventing the NULL pointer dereference.

Impact Analysis

This vulnerability can cause the Linux kernel to crash when handling certain wireless stations on AP_VLAN interfaces. Such a crash can lead to denial of service (DoS) conditions on affected systems, potentially disrupting network connectivity and impacting system stability.

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