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]

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-04-03

Last Modified

2026-05-20

Generated

2026-07-06

AI Q&A

2026-04-03

EPSS Evaluated

2026-07-05

NVD

CVE-2026-31394

EUVD

EUVD-2026-18770

Affected Vendors & Products

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

KEV

CWE ID	Description
CWE-476	The product dereferences a pointer that it expects to be valid but is NULL.

Attack-Flow Graph

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.

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.

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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