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CVE-2026-64568
wifi: mac80211: fix unsol_bcast_probe_resp double free on alloc failure
Published 2026-08-05 (2 months ago) by the Linux kernel CNA. Subsystem net/mac80211. Debian urgency: unimportant.
What to do, per Debian release
Debian's own status for CVE-2026-64568 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 | fixedDSA-6415-1 · 2026-08-06 · text | 6.12.101-1 | Update the kernel and reboot. DSA-6415-1 shipped the fix on 2026-08-06, in 6.12.101-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.6-1 | Update the kernel and reboot. Fixed in 7.1.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian 12bookworm · linux-6.12 | fixedDLA-4745-1 · 2026-08-18 · text | 6.12.101-1~deb12u1 | Update the kernel and reboot. DLA-4745-1 shipped the fix on 2026-08-18, in 6.12.101-1~deb12u1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
ieee80211_set_unsol_bcast_probe_resp() calls kfree_rcu() on the old template before allocating the replacement. If the kzalloc() then fails, it returns -ENOMEM while link->u.ap.unsol_bcast_probe_resp still points at the object already queued for freeing. A later update or AP teardown re-queues that same rcu_head; the second free is caught by KASAN when the RCU sheaf is processed in softirq: BUG: KASAN: double-free in rcu_free_sheaf (mm/slub.c:5850) Free of addr ffff88800d06f300 by task exploit/145 ... __rcu_free_sheaf_prepare (mm/slub.c:2634 mm/slub.c:2940) rcu_free_sheaf (mm/slub.c:5850) rcu_core (kernel/rcu/tree.c:2617 kernel/rcu/tree.c:2869) handle_softirqs (kernel/softirq.c:622) The buggy address belongs to the cache kmalloc-128 of size 128 Queue the old object for kfree_rcu() only after the new one is published, matching ieee80211_set_probe_resp() and ieee80211_set_s1g_short_beacon().
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.
net/mac80211/cfg.c
- What this is
- MAC80211MAINTAINERS section matched on net/mac80211/ · linux-wireless@vger.kernel.org · Maintained
- Kernel module
- mac80211
Check it on the machine
grep -w CONFIG_MAC80211 /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 mac80211Prints 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.
- bookwormMnot built on amd64/cloud-amd64, arm64/cloud-arm64
- trixie, forky, sidMnot built on amd64/cloud-amd64, arm64/cloud-arm64, s390x/s390x
- bookworm · linux-6.12Mnot built on amd64/cloud-amd64, arm64/cloud-arm64
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_MAC80211
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
- 2026-08-05 (2 months ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.12%, higher than 1.7% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- unimportantsource
- Subsystem
- net/mac80211
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.7 | 6.12.101 | ca27a81cd77b |
| 6.7 | 6.18.42 | d62b55b7c7dc |
| 6.7 | 7.1.6 | 0ace76e410d7 |
| 6.7 | 7.2 | 1d067abcd370 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4745-1 | 2026-08-18 | bookworm 6.12.101-1~deb12u1 | tracker |
| DSA-6415-1 | 2026-08-06 | trixie 6.12.101-1 | tracker |
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:LAttack vector, local
- Triggered only via local nl80211 SoftAP config (NL80211_CMD_START_AP/SET_BEACON/CHANNEL_SWITCH/COLOR_CHANGE → ieee80211_set_unsol_bcast_probe_resp), not by processing over-the-air WiFi frames or remote packets.
- AC:LAttack complexity, low
- The attacker fully controls the SET_BEACON/STOP_AP sequence and can force the GFP_KERNEL kzalloc failure (e.g. memory pressure/memcg) with an attacker-chosen template size; no race or condition outside attacker influence is required.
- PR:LPrivileges required, low
- START_AP and SET_BEACON use GENL_UNS_ADMIN_PERM (CAP_NET_ADMIN in the wiphy netns user_ns). Per CNA guidance that capability via user namespaces scores Low, not init-namespace root High.
- UI:NUser interaction, none
- The attacker issues the nl80211 commands to set the unsolicited broadcast probe response template and later tear down or update the AP; no separate victim action is required.
- S:UScope, unchanged
- Impact stays inside the host kernel mac80211 heap (local privilege-escalation class) and does not cross a VM, IOMMU, or other separate security authority.
- C:HConfidentiality impact, high
- After the failed alloc the dangling unsol_bcast_probe_resp pointer can be read via ieee80211_get_unsol_bcast_probe_resp_tmpl and the object is double-freed; double-free/UAF enables heap reuse and arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- Double-free of the attacker-sized kmalloc unsol_bcast_probe_resp template (and subsequent stop_ap/update re-free) is classic heap corruption enabling spray/arbitrary-write and control-flow hijack primitives.
- A:HAvailability impact, high
- The bug is a KASAN-confirmed double-free in rcu_free_sheaf softirq processing (task exploit/145) and can oops/panic the kernel, fully denying availability.