# CVE-2026-63871: Bluetooth: ISO: Fix data-race on iso_pi fields in hci_get_route calls

> A data race in the Linux kernel Bluetooth ISO subsystem allows local attackers to trigger a kernel crash via concurrent socket operations.

- **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:** 19 Jul 2026
- **Updated:** 19 Jul 2026
- **Also known as:** AZL-92570, BELL-CVE-2026-63871, DEBIAN-CVE-2026-63871, GHSA-5243-p4qj-j66v, ROOT-OS-DEBIAN-12-CVE-2026-63871, UBUNTU-CVE-2026-63871

## What is CVE-2026-63871?

CVE-2026-63871 is a vulnerability in Linux, published on 19 Jul 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: ISO: Fix data-race on iso_pi fields in hci_get_route calls

iso_connect_bis(), iso_connect_cis(), iso_listen_bis(), and
iso_conn_big_sync() call hci_get_route() using iso_pi(sk)->dst,
iso_pi(sk)->src, and iso_pi(sk)->src_type without holding lock_sock().

These fields may be modified concurrently by connect() or setsockopt()
on the same socket, resulting in data-races reported by KCSAN.

Fix this by snapshotting the required fields under lock_sock() before
calling hci_get_route().

BUG: KCSAN: data-race in memcmp+0x45/0xb0

race at unknown origin, with read to 0xffff8880122135cf of 1 bytes
by task 333 on cpu 1:
 memcmp+0x45/0xb0
 hci_get_route+0x27e/0x490
 iso_connect_cis+0x4c/0xa10
 iso_sock_connect+0x60e/0xb30
 __sys_connect_file+0xbd/0xe0
 __sys_connect+0xe0/0x110
 __x64_sys_connect+0x40/0x50
 x64_sys_call+0xcad/0x1c60
 do_syscall_64+0x133/0x590
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

## Which versions are affected by CVE-2026-63871?


## How do I fix CVE-2026-63871?

Apply the vendor's patch.

## Is CVE-2026-63871 being exploited?

There is no known exploitation of CVE-2026-63871 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-63871 and fix it if it is affected.

What it is: CVE-2026-63871 is a vulnerability in Linux, published on 19 Jul 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-2026-63871 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-2026-63871/ (Markdown: https://insights.sbomify.com/CVE-2026-63871/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-63871
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-63871
- OSV: https://osv.dev/vulnerability/CVE-2026-63871

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-63871/
Summaries are generated and may contain mistakes; the official description above is the record.