Look up another CVE · open CVE-2026-90381 in the interactive tracker
CVE-2026-90381
wifi: mt76: fix handling channel context with different bands in mt76_switch_vif_chanctx()
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-90381 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | not affected | 6.1.190-1 | Nothing to do. bookworm never shipped the vulnerable code. |
| Debian 13trixie | not affected | 6.12.113-1 | Nothing to do. trixie never shipped the vulnerable code. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
When performing channel switches on different radios within a short timeframe, channel contexts with different bands can be carried for each struct ieee80211_vif_chanctx_switch. Rework mt76_switch_vif_chanctx() to properly handle this scenario.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
drivers/net/wireless/mediatek/mt76/channel.c
- What this is
- MEDIATEK MT76 WIRELESS LAN DRIVERMAINTAINERS section matched on drivers/net/wireless/mediatek/mt76/ · linux-wireless@vger.kernel.org · Maintained
- Kernel module
- mt76
Check it on the machine
grep -wE 'CONFIG_MT76_CORE|CONFIG_WLAN|CONFIG_WLAN_VENDOR_MEDIATEK' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
lsmod | grep -w mt76Prints a line if that module is loaded right now, and nothing if it is not. One that is not loaded can still be loaded later by anything that needs it.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed. The build rule could not be established for 2 releases, so nothing is claimed about those.
- bookworm, trixie?
- forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- ?
- not established - no Makefile entry for the affected file
- M
- a module where it is built at all; some flavours do not build it
Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.
- Build switches
- CONFIG_MT76_CORE, CONFIG_WLAN, CONFIG_WLAN_VENDOR_MEDIATEK
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-17 (31 days ago)source
- CVSS
- 8.8 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.38%, higher than 29.9% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- drivers/net
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.14 | 6.18.57 | 7a1b971b799e |
| 6.14 | 7.2.6 | 063169a2755a |
| 6.14 | 7.3 | 70869cc429ff |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:AAttack vector, adjacent network
- CSA IEs in a received Beacon (ieee80211_rx_mgmt_beacon → ieee80211_sta_process_chanswitch → ieee80211_link_reserve_chanctx) or Channel Switch action frame (ieee80211_sta_rx_queued_mgmt) make ieee80211_chsw_switch_vifs call mt76_switch_vif_chanctx with one ieee80211_vif_chanctx_switch per radio; those 802.11 frames are radio-range, not a routable IP protocol.
- AC:LAttack complexity, low
- ieee80211_vif_use_reserved_switch returns -EAGAIN until every in-place reservation is reserved_ready, then ieee80211_chsw_switch_vifs batches them into one CHANCTX_SWMODE_SWAP_CONTEXTS call; an AP/MLD that puts CSA IEs on two mt7996 bands with matching counts makes both ready in order with no victim-only race.
- PR:NPrivileges required, none
- ieee80211_rx_mgmt_beacon only needs ieee80211_rx_our_beacon() BSSID match on an associated STA, and mt7996 sets CHANCTX_STA_CSA so this path is used; beacons are unauthenticated, so the AP or a radio-range BSSID spoof needs no Linux capability or account.
- UI:NUser interaction, none
- An already-associated station runs ieee80211_csa_switch_work → ieee80211_link_use_reserved_context when the CSA count elapses and automatically enters mt76_switch_vif_chanctx; no extra click, reconnect, or mount is required at trigger time.
- S:UScope, unchanged
- Aliased mlink->ctx, the leftover phy->chanctx on non-first radios, and any resulting host-kernel heap UAF stay inside this machine’s mt76/mac80211; no VM, IOMMU, or sandbox boundary is crossed.
- C:HConfidentiality impact, high
- The pre-fix function set every mlink->ctx to vifs[0].new_ctx. After that first ieee80211_chanctx is kfree_rcu’d (ieee80211_free_chanctx when the first vif/link unassigns while others remain), mt76_vif_link_phy() still does mlink->ctx->drv_priv and reads ctx->phy from the freed object, a kernel info-leak UAF.
- I:HIntegrity impact, high
- The same dangling mlink->ctx makes mt76_vif_link_phy() return ctx->phy from reallocatable freed ieee80211_chanctx memory; callers such as mt7996_link_info_changed then issue MCU updates (mt7996_mcu_add_bss_info and similar) through that forged mt76_phy pointer, a kernel write/control-flow primitive.
- A:HAvailability impact, high
- mt76_vif_link_phy() on the stale mlink->ctx oopses after the aliased chanctx is freed; the pre-fix path also skipped mt76_phy_update_channel for every radio but vifs[0], leaving that PHY’s phy->chanctx pointing at the old ctx that ieee80211_vif_use_reserved_switch kfree_rcu’s, taking the radio down.