# CVE-2024-26903: Bluetooth: rfcomm: Fix null-ptr-deref in rfcomm_check_security

> A race condition in the Linux kernel Bluetooth stack 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:** 17 Apr 2024
- **Updated:** 15 Oct 2026
- **Also known as:** AZL-40088, BELL-CVE-2024-26903, DEBIAN-CVE-2024-26903, GHSA-w69g-9g23-pfwc, UBUNTU-CVE-2024-26903

## What is CVE-2024-26903?

CVE-2024-26903 is a medium-severity vulnerability in Linux kernel, published on 17 Apr 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: rfcomm: Fix null-ptr-deref in rfcomm_check_security

During our fuzz testing of the connection and disconnection process at the
RFCOMM layer, we discovered this bug. By comparing the packets from a
normal connection and disconnection process with the testcase that
triggered a KASAN report. We analyzed the cause of this bug as follows:

1. In the packets captured during a normal connection, the host sends a
`Read Encryption Key Size` type of `HCI_CMD` packet
(Command Opcode: 0x1408) to the controller to inquire the length of
encryption key.After receiving this packet, the controller immediately
replies with a Command Completepacket (Event Code: 0x0e) to return the
Encryption Key Size.

2. In our fuzz test case, the timing of the controller's response to this
packet was delayed to an unexpected point: after the RFCOMM and L2CAP
layers had disconnected but before the HCI layer had disconnected.

3. After receiving the Encryption Key Size Response at the time described
in point 2, the host still called the rfcomm_check_security function.
However, by this time `struct l2cap_conn *conn = l2cap_pi(sk)->chan->conn;`
had already been released, and when the function executed
`return hci_conn_security(conn->hcon, d->sec_level, auth_type, d->out);`,
specifically when accessing `conn->hcon`, a null-ptr-deref error occurred.

To fix this bug, check if `sk->sk_state` is BT_CLOSED before calling
rfcomm_recv_frame in rfcomm_process_rx.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-26903?

It affects 1 product.


Products: Linux kernel.

## How do I fix CVE-2024-26903?

Apply the vendor's patch.

## Is CVE-2024-26903 being exploited?

There is no known exploitation of CVE-2024-26903 in the wild and no public exploit code.

## Other vulnerabilities in Linux kernel

- [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild)
- [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild)
- [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild)
- [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild)
- [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-26903 and fix it if it is affected.

What it is: CVE-2024-26903 is a medium-severity vulnerability in Linux kernel, published on 17 Apr 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-2024-26903 in the wild and no public exploit code.

Affected product: Linux kernel. 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-2024-26903/ (Markdown: https://insights.sbomify.com/CVE-2024-26903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-26903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-26903
- OSV: https://osv.dev/vulnerability/CVE-2024-26903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-26903/
Summaries are generated and may contain mistakes; the official description above is the record.