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CVE-2026-72003
wifi: brcmfmac: cyw: fix heap overflow on a short auth frame
Published 2026-08-15 (2 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-2026-72003 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 | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.1.5-1 | Update the kernel and reboot. Fixed in 7.1.5-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
brcmf_notify_auth_frame_rx() takes the frame length from the firmware event and copies the frame body with the management header offset subtracted: u32 mgmt_frame_len = e->datalen - sizeof(struct brcmf_rx_mgmt_data); ... memcpy(&mgmt_frame->u, frame, mgmt_frame_len - offsetof(struct ieee80211_mgmt, u)); The only length check is e->datalen >= sizeof(*rxframe), so mgmt_frame_len can be anything from 0 up. offsetof(struct ieee80211_mgmt, u) is 24. When mgmt_frame_len is below that, the subtraction wraps as an unsigned value to a huge length. The memcpy then runs far past the kzalloc'd buffer. A malicious or malfunctioning AP can make the frame short during the external SAE auth exchange, so this is a remotely triggered heap overflow. Reject frames shorter than the management header offset before the copy.
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/broadcom/brcm80211/brcmfmac/cyw/core.c
- What this is
- BROADCOM BRCM80211 IEEE802.11 WIRELESS DRIVERSMAINTAINERS section matched on drivers/net/wireless/broadcom/brcm80211/ · linux-wireless@vger.kernel.org · Supported
- Kernel module
- brcmfmac_cyw
Check it on the machine
grep -wE 'CONFIG_BRCMFMAC|CONFIG_BRCMSMAC|CONFIG_WLAN|CONFIG_WLAN_VENDOR_BROADCOM' /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 brcmfmac_cywPrints 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?
- 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_BRCMFMAC, CONFIG_BRCMSMAC, CONFIG_WLAN, CONFIG_WLAN_VENDOR_BROADCOM
- 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
- 2026-08-15 (2 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
- 0.35%, higher than 26.9% 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 |
|---|---|---|
| 6.16 | 6.18.40 | 55b26abb1fa1 |
| 6.16 | 7.1.5 | 185bb156c427 |
| 6.16 | 7.2 | 240c8d2c717b |
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
- A malicious or rogue AP on the same WiFi/BSS segment sends a truncated 802.11 authentication frame during the external SAE handshake; the brcmfmac CYW driver processes it from firmware events with no other network hop required.
- AC:LAttack complexity, low
- The attacker fully controls the AP and can reliably deliver auth frames with firmware-reported lengths below 24 bytes during SAE, triggering the unsigned underflow and huge memcpy without races or victim-specific heap layout.
- PR:NPrivileges required, none
- Exploitation requires no privileges on the victim host; an unauthenticated adjacent wireless attacker operating a rogue WPA3-SAE AP can trigger the pre-authentication code path without local access or capabilities.
- UI:NUser interaction, none
- No victim action is required at exploit time beyond normal station behavior; auto-reconnect or background association to a saved WPA3 network (or an evil-twin SSID) suffices to enter external SAE where the malicious auth frame is delivered.
- S:UScope, unchanged
- Impact is confined to kernel memory on the vulnerable station; successful exploitation yields local privilege escalation or denial of service on the same host, not a cross-VM or cross-security-authority boundary escape.
- C:HConfidentiality impact, high
- The underflowed memcpy length reads far beyond the firmware event buffer (kernel heap OOB read) and corrupts adjacent heap objects; such heap overflows are routinely weaponized for arbitrary kernel memory disclosure.
- I:HIntegrity impact, high
- The same memcpy writes gigabyte-scale data past the kzalloc allocation, corrupting kernel heap metadata and adjacent objects in ways that enable arbitrary write primitives and potential code execution.
- A:HAvailability impact, high
- Copying ~4 GiB from kernel memory reliably causes kernel oops, panic, or hang on the affected system; even failed exploitation typically crashes the host.