# CVE-2024-27399: Bluetooth: l2cap: fix null-ptr-deref in l2cap_chan_timeout
> A race condition in the Linux kernel Bluetooth L2CAP subsystem causes a null pointer dereference, leading to a system crash.
- **Severity:** Medium 5.5 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H`)
- **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:** 13 May 2024
- **Updated:** 11 May 2026
- **Also known as:** BELL-CVE-2024-27399, DEBIAN-CVE-2024-27399, GHSA-3p2h-8x46-gvg6, UBUNTU-CVE-2024-27399
## What is CVE-2024-27399?
CVE-2024-27399 is a medium-severity vulnerability in Debian Debian Linux, published on 13 May 2024. 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: l2cap: fix null-ptr-deref in l2cap_chan_timeout
There is a race condition between l2cap_chan_timeout() and
l2cap_chan_del(). When we use l2cap_chan_del() to delete the
channel, the chan->conn will be set to null. But the conn could
be dereferenced again in the mutex_lock() of l2cap_chan_timeout().
As a result the null pointer dereference bug will happen. The
KASAN report triggered by POC is shown below:
[ 472.074580] ==================================================================
[ 472.075284] BUG: KASAN: null-ptr-deref in mutex_lock+0x68/0xc0
[ 472.075308] Write of size 8 at addr 0000000000000158 by task kworker/0:0/7
[ 472.075308]
[ 472.075308] CPU: 0 PID: 7 Comm: kworker/0:0 Not tainted 6.9.0-rc5-00356-g78c0094a146b #36
[ 472.075308] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu4
[ 472.075308] Workqueue: events l2cap_chan_timeout
[ 472.075308] Call Trace:
[ 472.075308]
[ 472.075308] dump_stack_lvl+0x137/0x1a0
[ 472.075308] print_report+0x101/0x250
[ 472.075308] ? __virt_addr_valid+0x77/0x160
[ 472.075308] ? mutex_lock+0x68/0xc0
[ 472.075308] kasan_report+0x139/0x170
[ 472.075308] ? mutex_lock+0x68/0xc0
[ 472.075308] kasan_check_range+0x2c3/0x2e0
[ 472.075308] mutex_lock+0x68/0xc0
[ 472.075308] l2cap_chan_timeout+0x181/0x300
[ 472.075308] process_one_work+0x5d2/0xe00
[ 472.075308] worker_thread+0xe1d/0x1660
[ 472.075308] ? pr_cont_work+0x5e0/0x5e0
[ 472.075308] kthread+0x2b7/0x350
[ 472.075308] ? pr_cont_work+0x5e0/0x5e0
[ 472.075308] ? kthread_blkcg+0xd0/0xd0
[ 472.075308] ret_from_fork+0x4d/0x80
[ 472.075308] ? kthread_blkcg+0xd0/0xd0
[ 472.075308] ret_from_fork_asm+0x11/0x20
[ 472.075308]
[ 472.075308] ==================================================================
[ 472.094860] Disabling lock debugging due to kernel taint
[ 472.096136] BUG: kernel NULL pointer dereference, address: 0000000000000158
[ 472.096136] #PF: supervisor write access in kernel mode
[ 472.096136] #PF: error_code(0x0002) - not-present page
[ 472.096136] PGD 0 P4D 0
[ 472.096136] Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI
[ 472.096136] CPU: 0 PID: 7 Comm: kworker/0:0 Tainted: G B 6.9.0-rc5-00356-g78c0094a146b #36
[ 472.096136] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu4
[ 472.096136] Workqueue: events l2cap_chan_timeout
[ 472.096136] RIP: 0010:mutex_lock+0x88/0xc0
[ 472.096136] Code: be 08 00 00 00 e8 f8 23 1f fd 4c 89 f7 be 08 00 00 00 e8 eb 23 1f fd 42 80 3c 23 00 74 08 48 88
[ 472.096136] RSP: 0018:ffff88800744fc78 EFLAGS: 00000246
[ 472.096136] RAX: 0000000000000000 RBX: 1ffff11000e89f8f RCX: ffffffff8457c865
[ 472.096136] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff88800744fc78
[ 472.096136] RBP: 0000000000000158 R08: ffff88800744fc7f R09: 1ffff11000e89f8f
[ 472.096136] R10: dffffc0000000000 R11: ffffed1000e89f90 R12: dffffc0000000000
[ 472.096136] R13: 0000000000000158 R14: ffff88800744fc78 R15: ffff888007405a00
[ 472.096136] FS: 0000000000000000(0000) GS:ffff88806d200000(0000) knlGS:0000000000000000
[ 472.096136] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 472.096136] CR2: 0000000000000158 CR3: 000000000da32000 CR4: 00000000000006f0
[ 472.096136] Call Trace:
[ 472.096136]
[ 472.096136] ? __die_body+0x8d/0xe0
[ 472.096136] ? page_fault_oops+0x6b8/0x9a0
[ 472.096136] ? kernelmode_fixup_or_oops+0x20c/0x2a0
[ 472.096136] ? do_user_addr_fault+0x1027/0x1340
[ 472.096136] ? _printk+0x7a/0xa0
[ 472.096136] ? mutex_lock+0x68/0xc0
[ 472.096136] ? add_taint+0x42/0xd0
[ 472.096136] ? exc_page_fault+0x6a/0x1b0
[ 472.096136] ? asm_exc_page_fault+0x26/0x30
[ 472.096136] ? mutex_lock+0x75/0xc0
[ 472.096136] ? mutex_lock+0x88/0xc0
[ 472.096136] ? mutex_lock+0x75/0xc0
[ 472.096136] l2cap_chan_timeo
---truncated---
Weakness: CWE-476 (NULL Pointer Dereference)
## Which versions are affected by CVE-2024-27399?
It affects 3 products.
Products: Debian Debian Linux, Fedoraproject Fedora, Linux kernel.
## How do I fix CVE-2024-27399?
Apply the vendor's patch.
## Is CVE-2024-27399 being exploited?
There is no known exploitation of CVE-2024-27399 in the wild and no public exploit code.
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## Fix prompt for AI coding agents
```text
Check this codebase for CVE-2024-27399 and fix it if it is affected.
What it is: CVE-2024-27399 is a medium-severity vulnerability in Debian Debian Linux, published on 13 May 2024. 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-2024-27399 in the wild and no public exploit code.
Affected product: Debian Debian 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-2024-27399/ (Markdown: https://insights.sbomify.com/CVE-2024-27399/index.md)
```
## Sources
- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-27399
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-27399
- OSV: https://osv.dev/vulnerability/CVE-2024-27399
---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-27399/
Summaries are generated and may contain mistakes; the official description above is the record.