CVE-2024-26903

MEDIUM
Published Apr 17, 2024 Modified May 12, 2026 CWE-476

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.

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CVSS v3.1 Score

5.5
MEDIUM
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor Product
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel
linux linux_kernel

References

Advisories & Patches

https://git.kernel.org/stable/c/2535b848fa0f42ddff3e5255cf5e742c9b77bb26 https://git.kernel.org/stable/c/369f419c097e82407dd429a202cde9a73d3ae29b https://git.kernel.org/stable/c/3ead59bafad05f2967ae2438c0528d53244cfde5 https://git.kernel.org/stable/c/567c0411dc3b424fc7bd1e6109726d7ba32d4f73 https://git.kernel.org/stable/c/5f369efd9d963c1f711a06c9b8baf9f5ce616d85 https://git.kernel.org/stable/c/5f9fe302dd3a9bbc50f4888464c1773f45166bfd https://git.kernel.org/stable/c/81d7d920a22fd58ef9aedb1bd0a68ee32bd23e96 https://git.kernel.org/stable/c/8d1753973f598531baaa2c1033cf7f7b5bb004b0 https://git.kernel.org/stable/c/2535b848fa0f42ddff3e5255cf5e742c9b77bb26 https://git.kernel.org/stable/c/369f419c097e82407dd429a202cde9a73d3ae29b https://git.kernel.org/stable/c/3ead59bafad05f2967ae2438c0528d53244cfde5 https://git.kernel.org/stable/c/567c0411dc3b424fc7bd1e6109726d7ba32d4f73 https://git.kernel.org/stable/c/5f369efd9d963c1f711a06c9b8baf9f5ce616d85 https://git.kernel.org/stable/c/5f9fe302dd3a9bbc50f4888464c1773f45166bfd https://git.kernel.org/stable/c/81d7d920a22fd58ef9aedb1bd0a68ee32bd23e96 https://git.kernel.org/stable/c/8d1753973f598531baaa2c1033cf7f7b5bb004b0

Frequently Asked Questions

What is CVE-2024-26903? +
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. It has a CVSS v3.1 base score of 5.5 (MEDIUM).
How severe is CVE-2024-26903? +
CVE-2024-26903 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.
What products are affected by CVE-2024-26903? +
CVE-2024-26903 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2024-26903? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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