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CVE-2026-63866
wifi: mt76: mt7996: Clear wcid pointer in mt7996_mac_sta_deinit_link()
Published 2026-07-19 (3 months ago) by the Linux kernel CNA. Subsystem drivers/net. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-63866 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 | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.10-1 | Update the kernel and reboot. Fixed in 7.0.10-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Clear WCID pointer removing the sta link in mt7996_mac_sta_deinit_link routine.
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/mt7996/main.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
- mt7996e
Check it on the machine
grep -wE 'CONFIG_MT76_CORE|CONFIG_MT7996E|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 mt7996ePrints 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 1 release, so nothing is claimed about those.
- bookworm?
- trixieMnot built on amd64/cloud-amd64, arm64/cloud-arm64, armel/rpi, s390x/s390x
- 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_MT7996E, 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
- 2026-07-19 (3 months 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 |
|---|---|---|
| 6.15 | 6.18.33 | 455a48685fee |
| 6.15 | 7.0.10 | c575459b485c |
| 6.15 | 7.1 | 88973240dc7c |
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
- The bug is in the MediaTek mt7996 WiFi driver and is reached when MLO station links are torn down via mac80211's change_sta_links callback, which a remote WiFi peer can trigger through 802.11be MLO association/reconfiguration (malicious AP to a client, or a malicious associated client to an AP/router).
- AC:LAttack complexity, low
- An attacker who can complete or maintain an MLO WiFi session can deterministically trigger link removal/reconfiguration to hit mt7996_mac_sta_deinit_link(); no special memory layout or victim timing is required beyond normal MLO link churn the attacker controls.
- PR:NPrivileges required, none
- Exploitation requires no local OS privileges on the victim; the attacker only needs to act as a WiFi peer (e.g., malicious AP or associated MLO client) to drive mac80211 link changes into the driver, not root/CAP_NET_ADMIN on the target host.
- UI:NUser interaction, none
- No victim user action beyond normal automatic WiFi operation is required; link add/remove is driven by the attacker's 802.11 MLO signaling once the victim device is operating as a WiFi client or AP with MLO enabled.
- S:UScope, unchanged
- Impact is confined to kernel memory corruption and privilege escalation within the same kernel/host security boundary; this is not a VM escape, sandbox escape, or cross-authority boundary bypass.
- C:HConfidentiality impact, high
- Failing to NULL the global dev->mt76.wcid[idx] entry before mt76_wcid_mask_clear() and kfree_rcu() leaves a use-after-free; stale wcid pointers are dereferenced on RX/TX completion paths via mt76_wcid_ptr(), enabling arbitrary kernel memory reads.
- I:HIntegrity impact, high
- The dangling wcid pointer permits writes through subsequent TX/RX and wcid-based container_of lookups on freed mt7996_sta_link objects, giving attacker-influenced heap corruption primitives suitable for control-flow hijacking.
- A:HAvailability impact, high
- Use of a freed wcid structure during packet TX completion or RX processing can cause kernel oops/panic or wedged WiFi subsystem, and UAF corruption alone satisfies High availability impact even before full exploitation.