Cloudanix VulnDB

CVE-2026-99012

High · 7.8

CVSS

7.8

EPSS

0.2%

Published

Oct 23, 2026

CISA due date

—

Cloudanix analysis

Next patch cycle SSVC: Track

A flaw in the Linux kernel's Bluetooth handling lets a local user trigger crashes or gain elevated access by making overlapping connection attempts on certain wireless sockets.

Exploitation
Local Privilege
Attacker needs
Low Privilege
Complexity
Moderate
Impact
Full Compromise
Component
OS kernel
Class
Race Condition
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Race condition in iso_sock_connect allows concurrent callers to bypass admission checks, overwrite socket destination and connection pointers, and trigger use-after-free during teardown or callbacks when the socket lock is released between state checks and connection setup.

Why it matters to the business

Local users on affected Linux systems can trigger kernel crashes or memory corruption via Bluetooth ISO sockets, leading to denial of service or potential privilege escalation; widespread exposure in Bluetooth-enabled devices and servers increases operational risk until kernels are updated.

How an attack unfolds

A local attacker opens or binds an ISO socket and issues two concurrent connect calls; both pass the unlocked state check, one overwrites the destination or conn pointer of the other, and later teardown or HCI callbacks access freed socket memory, demonstrated by KASAN reports on slab-use-after-free.

How to fix it

Apply the upstream Linux kernel fix that performs admission checks under the socket lock, sets a connect-in-progress flag before publishing destination or attachment, rejects concurrent attempts with -EBADFD, and ensures proper reference handling in __iso_chan_add and iso_conn_add; rebuild and reboot with the patched kernel.

How to confirm the fix worked

Confirm the patch is present by inspecting iso_sock.c for the new flag checks and lock-protected admission logic; recompile a test kernel and run concurrent connect workloads under KASAN to verify absence of use-after-free reports.

Typical attack path

  1. Open or bind an ISO socket from a local process
  2. Issue two concurrent iso_sock_connect calls before either completes
  3. Trigger route selection and connection attachment that overwrites shared state
  4. Force connection failure or teardown to invoke callbacks on freed objects
  5. Observe or exploit the resulting use-after-free for crash or code execution

How to detect it

Search kernel logs and audit trails for KASAN use-after-free reports mentioning iso_sock_hold, iso_conn_del, or iso_connect_cfm; look for repeated failed ISO connection attempts from the same process or unusual Bluetooth HCI abort sequences preceding a crash.

What your security team should do

  • Prioritize kernel updates on all systems exposing Bluetooth ISO sockets within the next 30 days
  • Disable Bluetooth ISO functionality via kernel config or runtime disablement where not required
  • Monitor for local privilege-escalation attempts on multi-user or containerized Linux hosts
  • Add kernel build and boot tests that exercise concurrent ISO connect paths

The record

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: ISO: Serialize concurrent connect calls iso_sock_connect() checks the socket state before taking the socket lock and drops the lock again before setting up a connection. Two callers can both pass the admission check while the socket is open or bound. Caller A can copy its destination for route selection, then caller B can replace the socket destination before A binds or connects the CIS. A then uses B's destination with the route selected for its own request. B can also proceed after A attaches a connection and sets BT_CONNECT. For deferred BIS setup, B can bind a second BIS and overwrite iso_pi(sk)->conn, leaving the first connection's reference and conn->sk back-pointer stranded. Concurrent CIS connects can likewise replace the socket's connection. Later teardown only detaches the current connection, so a callback on the old connection can race with socket release and access a freed socket. KASAN reported: BUG: KASAN: slab-use-after-free in iso_sock_hold+0xf7/0x1b0 Call Trace: iso_sock_hold+0xf7/0x1b0 iso_conn_del+0x7b/0x1d0 iso_connect_cfm+0x186/0x16a0 hci_conn_failed+0x154/0x280 hci_abort_conn_sync+0x3dc/0x7d0 hci_cmd_sync_work+0x173/0x300 Allocated by task 121: sk_alloc+0x2b/0x6d0 bt_sock_alloc+0x29/0x370 iso_sock_alloc.constprop.0+0x19/0x300 iso_sock_create+0x94/0x100 Freed by task 121: kfree+0x121/0x3c0 __sk_destruct+0x42b/0x540 iso_sock_release+0x29d/0x340 __sock_release+0xa1/0x260 Check admission under the socket lock and mark the connect operation in progress before publishing its destination. Keep that flag set across route lookup and connection setup, rejecting another connect with -EBADFD before it can change the destination or attach a connection. Clear the flag after either helper returns, including on failure, so a failed setup can be retried. A separate flag is needed because the socket lock must be released before acquiring the HCI device lock, while BT_CONNECT requires an attached connection. Keep the existing state transitions and the deferred CIS completion through iso_sock_recvmsg(). Reject an existing socket attachment in __iso_chan_add() before taking a new reference or publishing either pointer, so every caller preserves the connection association. Keep the same-socket, same-connection success case for deferred CIS setup. Reject an attached socket before BIS setup so a reusable BIS is not claimed before the attachment is rejected. In CIS setup, reject a different HCI connection before iso_conn_add() and drop the per-attempt HCI hold directly. An unowned iso_conn may still carry another reference after detachment, so its destruction cannot be relied on to release that hold. iso_listen_bis() creates a fresh PA HCI/ISO pair under the device lock, so the temporary iso_conn_put() frees the ISO candidate and drops its HCI hold on rejection. iso_conn_ready() uses a freshly allocated, unpublished child with no connection, making the socket-side rejection unreachable.

Affected packages

Ecosystem Package Introduced Fixed