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CVE-2026-74300
Bluetooth: hci: validate codec capability element length
Published 2026-08-15 (2 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-2026-74300 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 | fixed | 6.1.180-1 | Update the kernel and reboot. Fixed in 6.1.180-1. A running kernel keeps the old code until the machine restarts. |
| Debian 13trixie | fixed | 6.12.100-1 | Update the kernel and reboot. Fixed in 6.12.100-1. A running kernel keeps the old code until the machine restarts. |
| 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
Read Local Codec Capabilities returns a sequence of capability elements. Each element starts with a one-byte length followed by that many payload bytes. hci_read_codec_capabilities() checks that the skb contains the length byte, but then validates only caps->len against the remaining skb length. A malformed controller response with one remaining byte and caps->len set to one passes that check even though the element needs two bytes. The parser then records a two-byte capability and copies one byte beyond the advertised response payload into the codec list. Validate the full element size, including the length byte, before adding it to the accumulated capability length. This preserves all well-formed capability elements and drops only truncated controller responses.
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_codec.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
- 2026-08-15 (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
- 0.40%, higher than 33.0% 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 |
|---|---|---|
| 5.16 | 6.1.178 | fc97fc8cf7f5 |
| 5.16 | 6.6.145 | 290b36f9d1eb |
| 5.16 | 6.12.97 | f2ad01f55e07 |
| 5.16 | 6.18.40 | ec4d352747a6 |
| 5.16 | 7.1.5 | 4bc16db0f119 |
| 5.16 | 7.2 | c38fbcdc4079 |
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 parsing HCI Read Local Codec Capabilities command-complete data from the Bluetooth controller during HCI adapter initialization; a nearby attacker who compromises or impersonates the controller (integrated phone BT, laptop adapter, automotive head unit) can deliver malformed responses over the Bluetooth hardware link.
- AC:LAttack complexity, low
- Exploitation only requires crafting controller response fields (num_caps and per-element length bytes) that pass the flawed length check; no races, timing windows, or victim-specific memory layout are needed, and the attacker fully controls the malformed HCI payload.
- PR:NPrivileges required, none
- No privileges on the victim host are required; the kernel issues the HCI commands during automatic Bluetooth bring-up and trusts controller replies, so an external adjacent attacker supplying malicious controller responses needs no local account, capabilities, or user-namespace admin rights.
- UI:NUser interaction, none
- Triggering occurs during HCI device initialization when Bluetooth is powered on, which is automatic at boot or through normal always-on Bluetooth use on phones, headsets, and vehicles, without any special victim action beyond routine Bluetooth operation.
- S:UScope, unchanged
- Impact is confined to kernel memory handling within the host Bluetooth stack during codec enumeration; it does not cross a security boundary such as VM escape, container breakout, or IOMMU/DMA isolation bypass.
- C:HConfidentiality impact, high
- The inflated capability length causes memcpy in hci_codec_list_add to read beyond the HCI response skb into adjacent kernel memory, leaking up to hundreds of bytes per response into permanently cached codec_list entries that can later be exposed via BT_CODEC socket queries.
- I:HIntegrity impact, high
- Out-of-bounds kernel heap access during parsing constitutes memory corruption; attacker-controlled lengths pollute kernel codec capability cache state and the same class of length-validation bugs in Bluetooth HCI parsing is routinely chained into further kernel compromise.
- A:HAvailability impact, high
- Reading past the skb tail can provoke kernel faults or panics on strict memory-sanitizer builds, and corrupted codec enumeration during hci_dev_open_sync can abort Bluetooth initialization, denying Bluetooth availability until reboot or adapter reset.