Bug 2454814 (CVE-2026-31394)

Summary: CVE-2026-31394 kernel: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in the Linux kernel's mac80211 component. This vulnerability occurs when processing stations on AP_VLAN interfaces, such as 4-address Wireless Distribution System (WDS) clients. An attacker could trigger a null pointer dereference during Channel Switch Announcement (CSA) operations, leading to a system crash and a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-04-03 16:02:12 UTC 
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]
Comment 1 Jon Moroney 2026-04-03 19:11:32 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026040325-CVE-2026-31394-26ac@gregkh/T