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CVE-2026-53209
Bluetooth: hci_sync: reject oversized Broadcast Announcement prepend
Published 2026-06-25 (4 months ago) by the Linux kernel CNA. Subsystem net/bluetooth. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-53209 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 | fixedDLA-4665-1 · 2026-07-03 · text | 6.1.176-1 | Update the kernel and reboot. DLA-4665-1 shipped the fix on 2026-07-03, in 6.1.176-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.94-1 | Update the kernel and reboot. Fixed in 6.12.94-1. A running kernel keeps the old code until the machine restarts. |
| Debian 14forky | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.0.13-1 | Update the kernel and reboot. Fixed in 7.0.13-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
Existing advertising instances can already hold the maximum extended advertising payload. When hci_adv_bcast_annoucement() prepends the Broadcast Announcement service data to that payload, the combined data may no longer fit in the temporary buffer used to rebuild the advertising data. Reject that case before copying the existing payload and report the failure through the device log. This keeps the existing advertising data intact and avoids overrunning the temporary buffer.
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/bluetooth/hci_sync.c
- What this is
- BLUETOOTH SUBSYSTEMMAINTAINERS section matched on net/bluetooth/ · linux-bluetooth@vger.kernel.org · Supported
- Kernel module
- bluetooth
Check it on the machine
grep -w CONFIG_BT /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 bluetoothPrints 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
- M
- a module where it is built at all; some flavours do not build it
- Build switch
- CONFIG_BT
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
- 2026-06-25 (4 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
- 0.13%, higher than 2.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- net/bluetooth
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.1.142 | 6.1.176 | 10b0e832cc05 |
| 6.6.94 | 6.6.143 | 1338ee049a89 |
| 6.12.34 | 6.12.94 | 02f50e8bb69f |
| 6.16 | 6.18.36 | dafc9f57140e |
| 6.16 | 7.0.13 | cdd8bbdbee76 |
| 6.16 | 7.1 | 5c65b96b549e |
| 6.15.3 | 0 | 0 |
Debian advisories
| Advisory | Date | Shipped to | Debian |
|---|---|---|---|
| DLA-4671-1 | 2026-07-05 | bullseye 6.1.176-1~deb11u1 | tracker |
| DLA-4665-1 | 2026-07-03 | bookworm 6.1.176-1 | 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
- The vulnerable path is reached through local AF_BLUETOOTH HCI management/ISO socket operations that configure advertising data and start BIS/periodic advertising. It is not reachable directly from Bluetooth radio packets sent by an adjacent attacker.
- AC:LAttack complexity, low
- The attacker can choose the advertising payload length/content, omit an existing Broadcast Announcement, provide BASE data that creates Basic Audio Announcement periodic data, and trigger the prepend deterministically. The needed Bluetooth LE Audio/extended advertising support is a reasonable affected deployment condition.
- PR:LPrivileges required, low
- The advertising setup path requires a trusted HCI management socket via CAP_NET_ADMIN, but the code uses capable() and is therefore reachable by a basic local user with CAP_NET_ADMIN obtained in a user namespace on systems allowing unprivileged user namespaces. ISO socket triggering itself has no stronger privilege gate.
- UI:NUser interaction, none
- No victim action is required once the local attacker can issue the Bluetooth socket operations. The attacker performs both setup and trigger steps directly.
- S:UScope, unchanged
- The corruption occurs in kernel Bluetooth code and affects the same kernel security authority. This is a standard local kernel memory-corruption scenario, not a VM/IOMMU or other cross-scope boundary escape.
- C:HConfidentiality impact, high
- The bug is an attacker-controlled kernel stack out-of-bounds write, and such memory corruption can plausibly be leveraged beyond a simple crash in less hardened configurations. Under the required uncertainty rule, confidentiality impact is scored high.
- I:HIntegrity impact, high
- The vulnerable memcpy writes past a fixed 251-byte stack buffer with attacker-controlled advertising bytes. Out-of-bounds kernel writes are scored as high integrity impact because they may enable control-flow or data corruption.
- A:HAvailability impact, high
- At minimum, the overflow can corrupt stack state or trigger hardening checks such as stack protector/FORTIFY, causing an oops or panic. The attacker can repeat the local trigger to deny service.