Look up another CVE · open CVE-2026-53254 in the interactive tracker
CVE-2026-53254
Bluetooth: RFCOMM: validate skb length in MCC handlers
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-2026-53254 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
The RFCOMM MCC handlers cast skb->data to protocol-specific structs without validating skb->len first. A malicious remote device can send truncated MCC frames and trigger out-of-bounds reads in these handlers. Fix this by using skb_pull_data() to validate and access the required data before dereferencing it. rfcomm_recv_rpn() requires special handling since ETSI TS 07.10 allows 1-byte RPN requests. Handle this by validating only the DLCI byte first, and validating the full struct only when len > 1.
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/rfcomm/core.c
- What this is
- BLUETOOTH SUBSYSTEMMAINTAINERS section matched on net/bluetooth/ · linux-bluetooth@vger.kernel.org · Supported
- Kernel module
- rfcomm
Check it on the machine
grep -wE 'CONFIG_BT|CONFIG_BT_RFCOMM' /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 rfcommPrints 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 switches
- CONFIG_BT, CONFIG_BT_RFCOMM
- 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
- 2026-06-25 (4 months ago)source
- CVSS
- 8.1 high
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:Hsource recompute it - Attack vector
- adjacent network (AV:A)source
- EPSS
- 0.27%, higher than 18.5% 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 |
|---|---|---|
| 2.6.12 | 5.15.210 | 7c15c7c28789 |
| 2.6.12 | 6.1.176 | 0d637136ce89 |
| 2.6.12 | 6.6.143 | 98377e6b1a1a |
| 2.6.12 | 6.12.94 | 1b070ac9e99c |
| 2.6.12 | 6.18.36 | 3eabc6d47a0a |
| 2.6.12 | 7.0.13 | 08b9c1fbe78f |
| 2.6.12 | 7.1 | 23882b828c3c |
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:AAttack vector, adjacent network
- An attacker reaches the vulnerable RFCOMM MCC parsing code by sending malformed Bluetooth RFCOMM frames over a BR/EDR L2CAP connection. Bluetooth requires radio adjacency rather than ordinary IP network reachability.
- AC:LAttack complexity, low
- The attacker controls the RFCOMM frame contents and can send truncated MCC frames directly after establishing the Bluetooth/L2CAP connection. No race or condition outside the attacker’s control is required.
- PR:NPrivileges required, none
- The RFCOMM L2CAP listener uses the SDP/low-security path, and the vulnerable control-channel parsing occurs before RFCOMM DLC/service-level authentication. A malicious nearby Bluetooth device does not need local privileges or authenticated credentials.
- UI:NUser interaction, none
- No victim action is needed once the target Bluetooth stack is reachable and accepting RFCOMM/L2CAP traffic. The attacker sends the malformed frames directly.
- S:UScope, unchanged
- The impact is within the Linux kernel Bluetooth/RFCOMM security authority. There is no VM escape, IOMMU bypass, or separate security scope crossed.
- C:HConfidentiality impact, high
- The bug is an out-of-bounds read from kernel skb memory, and some handler paths can reflect values derived from parsed control fields back to the peer. Under the required higher-severity rule, this is scored as high confidentiality impact.
- I:NIntegrity impact, none
- The fix and code review show bounded out-of-bounds reads, not an out-of-bounds write, use-after-free, or control-flow corruption primitive. Any state changes are limited to RFCOMM negotiation for the attacker-controlled connection.
- A:HAvailability impact, high
- Malformed short Bluetooth frames can trigger kernel out-of-bounds reads in the RFCOMM receive thread, with related Bluetooth short-frame bugs producing KASAN slab-out-of-bounds reports. Under kernel scoring guidance, such remotely triggerable kernel fault conditions are high availability impact.