# CVE-2026-98736: Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

> A use-after-free in the Linux kernel Bluetooth subsystem allows local attackers to execute arbitrary code or escalate privileges via race conditions during SCO setup.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-109028, BELL-CVE-2026-98736, DEBIAN-CVE-2026-98736, GHSA-jxf9-629p-pmqw, UBUNTU-CVE-2026-98736

## What is CVE-2026-98736?

CVE-2026-98736 is an use after free vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

Bluetooth: hci_conn: Lock parent access during enhanced SCO setup

hci_enhanced_setup_sync() runs on the request workqueue without the
hci_dev_lock held by its caller when setup was queued. Its CVSD
capability check and find_next_esco_param() dereference conn->parent
while the receive workqueue can unlink and release that parent.

The following interleaving can cause a use-after-free:

  hci_enhanced_setup_sync()       hci_disconn_complete_evt()
  load conn->parent
                                 hci_dev_lock()
                                 hci_conn_del(ACL parent)
                                   unlink SCO child
                                   drop link's parent reference
                                   clear child->parent
                                   release ACL parent
                                     bt_link_release()
                                       kfree(parent)
                                 hci_dev_unlock()
  read parent->features[0][3]

The reference held for the queued SCO child does not keep its ACL parent
alive after unlinking. Commit 42de40abe25d ("Bluetooth: hci_conn: fix the
SCO setup context lifetime") protects the child stored in the queued
context, but leaves these parent accesses unprotected.

With a 40 ms diagnostic delay after loading conn->parent, an instrumented
kernel based on fd179f8a05be, which already contains 42de40abe25d,

  BUG: KASAN: slab-use-after-free in hci_enhanced_setup_sync+0xda5/0xdf0
  Read of size 1 at addr ffff888102204047 by task kworker/u17:0/93
  Call Trace:
   hci_enhanced_setup_sync+0xda5/0xdf0
   hci_cmd_sync_work+0x13c/0x290
   process_one_work+0x6b4/0x10e0

  Allocated by task 92:
   __hci_conn_add+0x304/0x1df0
   hci_connect_acl+0x349/0x3e0
   hci_connect_sco+0x3b/0x9a0
   sco_sock_connect+0x475/0xca0

  Freed by task 94:
   kfree+0x121/0x3c0
   bt_link_release+0x79/0xa0
   device_release+0xc8/0x240
   kobject_put+0x14d/0x280
   hci_conn_del+0x524/0xe30
   hci_disconn_complete_evt+0x403/0x8c0
   hci_event_packet+0x71b/0xb20
   hci_rx_work+0x293/0x730

The accessed address is 71 bytes into the freed ACL parent, at its
features[0][3] byte; the queued SCO child is a different object. The
diagnostic preserves the loaded parent across the delay, matching the
unmodified compiled capability check, and does not change the parent
references or teardown path.

Hold hci_dev_lock() across the codec switch, including every call to
find_next_esco_param(), and release it on all selection errors. Keep
configure_datapath_sync() outside the critical section because it waits
for HCI events. Preserve parameter selection and existing return values.

## Which versions are affected by CVE-2026-98736?


## How do I fix CVE-2026-98736?

Apply the vendor's patch.

## Is CVE-2026-98736 being exploited?

There is no known exploitation of CVE-2026-98736 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98736 and fix it if it is affected.

What it is: CVE-2026-98736 is an use after free vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-98736 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-98736/ (Markdown: https://insights.sbomify.com/CVE-2026-98736/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98736
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98736
- OSV: https://osv.dev/vulnerability/CVE-2026-98736

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98736/
Summaries are generated and may contain mistakes; the official description above is the record.