In the Linux kernel, the following vulnerability has been resolved: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations… (CVE-2026-31394)
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]
AI Analysis
Technical Summary
The Linux kernel mac80211 subsystem contained a vulnerability (CVE-2026-31394) where the function ieee80211_chan_bw_change() iterates over stations and accesses link->reserved.oper via sta->sdata->link[link_id]. For AP_VLAN stations, sta->sdata points to a VLAN sdata whose link does not participate in channel context reservations, leaving link->reserved.oper zero-initialized with chan == NULL. This leads to a NULL pointer dereference in __ieee80211_sta_cap_rx_bw() when accessing chandef->chan->band during channel switch announcements (CSA). The fix involves resolving the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data, preventing the crash. The vulnerability affects Linux kernel versions prior to 6.8.0-1061.64~22.04.1 and related builds. The issue is addressed in official Ubuntu security updates (USN-8567-1, USN-8574-1) with patches available.
Potential Impact
The vulnerability causes a NULL pointer dereference leading to a crash in the Linux kernel's mac80211 wireless subsystem when handling AP_VLAN stations during channel bandwidth changes. This results in a denial of service condition affecting system availability. There is no indication of confidentiality or integrity impact. The CVSS v3.1 score is 5.5 (medium severity), reflecting local attack vector with low complexity and no user interaction required, causing an availability impact only.
Mitigation Recommendations
A patch is available and has been released by the vendor. Users should update their Linux kernel to versions 6.8.0-1061.64~22.04.1 or later (and related patched builds) as provided in the official Ubuntu security notices USN-8567-1 and USN-8574-1. After updating, a system reboot is required to apply the fix. Due to an ABI change, third-party kernel modules must be recompiled and reinstalled. Follow vendor instructions for updating and recompiling kernel modules to fully mitigate the vulnerability.
In the Linux kernel, the following vulnerability has been resolved: mac80211: fix crash in ieee80211_chan_bw_change for AP_VLAN stations… (CVE-2026-31394)
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 v3.1
Score 5.5medium
Affected software
pkg:deb/ubuntu/[email protected]?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/[email protected]?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/[email protected]~14.04.1?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/[email protected]~14.04.1?arch=source&distro=esm-infra-legacy/trustypkg:deb/ubuntu/[email protected]?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email protected]?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email protected]~16.04.1?arch=source&distro=xenialpkg:deb/ubuntu/[email protected]?arch=source&distro=esm-infra-legacy/xenialpkg:deb/ubuntu/[email 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protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingpkg:deb/ubuntu/[email protected]?arch=source&distro=questingRun on your own infrastructure? 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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The Linux kernel mac80211 subsystem contained a vulnerability (CVE-2026-31394) where the function ieee80211_chan_bw_change() iterates over stations and accesses link->reserved.oper via sta->sdata->link[link_id]. For AP_VLAN stations, sta->sdata points to a VLAN sdata whose link does not participate in channel context reservations, leaving link->reserved.oper zero-initialized with chan == NULL. This leads to a NULL pointer dereference in __ieee80211_sta_cap_rx_bw() when accessing chandef->chan->band during channel switch announcements (CSA). The fix involves resolving the VLAN sdata to its parent AP sdata using get_bss_sdata() before accessing link data, preventing the crash. The vulnerability affects Linux kernel versions prior to 6.8.0-1061.64~22.04.1 and related builds. The issue is addressed in official Ubuntu security updates (USN-8567-1, USN-8574-1) with patches available.
Potential Impact
The vulnerability causes a NULL pointer dereference leading to a crash in the Linux kernel's mac80211 wireless subsystem when handling AP_VLAN stations during channel bandwidth changes. This results in a denial of service condition affecting system availability. There is no indication of confidentiality or integrity impact. The CVSS v3.1 score is 5.5 (medium severity), reflecting local attack vector with low complexity and no user interaction required, causing an availability impact only.
Mitigation Recommendations
A patch is available and has been released by the vendor. Users should update their Linux kernel to versions 6.8.0-1061.64~22.04.1 or later (and related patched builds) as provided in the official Ubuntu security notices USN-8567-1 and USN-8574-1. After updating, a system reboot is required to apply the fix. Due to an ABI change, third-party kernel modules must be recompiled and reinstalled. Follow vendor instructions for updating and recompiling kernel modules to fully mitigate the vulnerability.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-31394
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:Pro:14.04:LTS","Ubuntu:Pro:16.04:LTS","Ubuntu:16.04:LTS","Ubuntu:Pro:FIPS:16.04:LTS","Ubuntu:Pro:18.04:LTS","Ubuntu:18.04:LTS","Ubuntu:Pro:FIPS-updates:18.04:LTS","Ubuntu:Pro:FIPS:18.04:LTS","Ubuntu:Pro:20.04:LTS","Ubuntu:20.04:LTS","Ubuntu:Pro:FIPS-updates:20.04:LTS","Ubuntu:Pro:FIPS:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:Nvidia-BlueField:22.04:LTS","Ubuntu:Pro:FIPS-preview:22.04:LTS","Ubuntu:Pro:FIPS-updates:22.04:LTS","Ubuntu:Pro:Realtime:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:Nvidia-BlueField:24.04:LTS","Ubuntu:Pro:FIPS-updates:24.04:LTS","Ubuntu:Pro:Realtime:24.04:LTS","Ubuntu:25.10"]
- Cvss Version
- 3.1
Threat ID: 6a5b626f2d1edb114c88d661
Added to database: 07/18/2026, 11:24:31 UTC
Last enriched: 08/01/2026, 06:01:58 UTC
Last updated: 09/14/2026, 22:01:33 UTC
Views: 19
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