Cloudanix VulnDB

CVE-2026-68188

None

CVSS

—

EPSS

0.2%

Published

Aug 10, 2026

CISA due date

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Cloudanix analysis

Next patch cycle SSVC: Track

A flaw in the Linux kernel's Bluetooth code can let a local user crash the system or possibly gain higher privileges by racing two internal operations that manage wireless serial connections.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Moderate
Impact
Privilege Gain
Component
OS kernel
Class
Use After Free
Remediation
Patch
Effort
Medium
Patch risk
Low

What it actually does

Race condition allows a TTY ioctl path to dereference a freed RFCOMM session structure after krfcommd removes the DLC under the mutex, resulting in slab use-after-free during rfcomm_send_rpn access of session->initiator and session->sock.

Why it matters to the business

Local attackers can trigger kernel memory corruption on systems exposing RFCOMM Bluetooth TTY devices, potentially leading to crashes or privilege escalation; high prevalence in Linux kernels with Bluetooth support increases exposure across servers, desktops, and embedded devices.

How an attack unfolds

An attacker opens an RFCOMM TTY device, issues a termios ioctl from one thread while the kernel's rfcomm_run thread concurrently closes the DLC and frees the session; the ioctl path then reads from the freed session pointer inside rfcomm_send_rpn, causing the UAF.

How to fix it

Upgrade to a kernel containing the fix that introduces rfcomm_dlc_send_rpn() under rfcomm_mutex protection; rebuild and reboot all affected systems; disable RFCOMM TTY support via kernel config if Bluetooth serial emulation is unused.

How to confirm the fix worked

Confirm presence of the patched rfcomm_dlc_send_rpn helper and removal of the unlocked dlc->session test in rfcomm_tty_set_termios; run syzkaller or KASAN-enabled reproducers targeting RFCOMM termios ioctls; verify no KASAN reports on session dereference paths.

Typical attack path

  1. Open /dev/rfcommX or equivalent RFCOMM TTY device
  2. Spawn concurrent thread that triggers DLC teardown via rfcomm_session_del
  3. Issue TIOCSETA/TIOCMGET-style termios ioctl from attacker thread
  4. Trigger rfcomm_tty_set_termios -> rfcomm_send_rpn on stale dlc->session pointer
  5. Read or write through freed session object to corrupt kernel memory

How to detect it

Search kernel logs for KASAN slab-use-after-free reports citing rfcomm_send_rpn or rfcomm_tty_set_termios; monitor for unusual sequences of RFCOMM session creation followed immediately by termios ioctls from unprivileged processes.

What your security team should do

  • Prioritize kernel updates on any host with Bluetooth RFCOMM enabled
  • Audit kernel configs to disable CONFIG_BT_RFCOMM_TTY when not required
  • Add runtime monitoring for Bluetooth TTY creation events in high-risk environments
  • Test patched kernels with Bluetooth stress workloads before broad deployment

The record

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: RFCOMM: Fix session UAF in set_termios rfcomm_tty_set_termios() tests dlc->session without rfcomm_mutex and later passes the pointer to rfcomm_send_rpn(). The latter dereferences both session->initiator and session->sock. Meanwhile, krfcommd can unlink the DLC and free the session while holding rfcomm_mutex. The race can proceed as follows: TTY ioctl task krfcommd -------------- -------- load dlc->session enter rfcomm_send_rpn() lock rfcomm_mutex clear dlc->session free session unlock rfcomm_mutex read session->initiator KASAN reported: BUG: KASAN: slab-use-after-free in rfcomm_send_rpn+0x297/0x2a0 Read of size 4 at addr ffff88810012a850 by task poc/92 Call Trace: rfcomm_send_rpn+0x297/0x2a0 rfcomm_tty_set_termios+0x50d/0x850 tty_set_termios+0x596/0x950 set_termios+0x46a/0x6e0 tty_mode_ioctl+0x152/0xbd0 tty_ioctl+0x915/0x1240 __x64_sys_ioctl+0x134/0x1c0 Allocated by task 92: rfcomm_session_add+0x9e/0x2e0 rfcomm_dlc_open+0x8b1/0xe00 rfcomm_dev_activate+0x85/0x1a0 rfcomm_tty_open+0x90/0x280 Freed by task 68: kfree+0x131/0x3c0 rfcomm_session_del+0x119/0x180 rfcomm_run+0x737/0x4710 Add rfcomm_dlc_send_rpn(), which holds rfcomm_mutex while it verifies that the DLC is still attached and sends the RPN frame. Have the TTY path use the helper and drop its unlocked session check. This keeps the session valid through both the frame construction and socket send.

Affected packages

Ecosystem Package Introduced Fixed