CVE-2025-39889

In the Linux kernel, the following vulnerability has been resolved:

Bluetooth: l2cap: Check encryption key size on incoming connection

This is required for passing GAP/SEC/SEM/BI-04-C PTS test case:

Security Mode 4 Level 4, Responder - Invalid Encryption Key Size

- 128 bit

This tests the security key with size from 1 to 15 bytes while the

Security Mode 4 Level 4 requests 16 bytes key size.

Currently PTS fails with the following logs:

- expected:Connection Response:

Code: [3 (0x03)] Code

Identifier: (lt)WildCard: Exists(gt)

Length: [8 (0x0008)]

Destination CID: (lt)WildCard: Exists(gt)

Source CID: [64 (0x0040)]

Result: [3 (0x0003)] Connection refused - Security block

Status: (lt)WildCard: Exists(gt),

but received:Connection Response:

Code: [3 (0x03)] Code

Identifier: [1 (0x01)]

Length: [8 (0x0008)]

Destination CID: [64 (0x0040)]

Source CID: [64 (0x0040)]

Result: [0 (0x0000)] Connection Successful

Status: [0 (0x0000)] No further information available

And HCI logs:

< HCI Command: Read Encrypti.. (0x05|0x0008) plen 2

Handle: 14 Address: 00:1B:DC:F2:24:10 (Vencer Co., Ltd.)

> HCI Event: Command Complete (0x0e) plen 7

Read Encryption Key Size (0x05|0x0008) ncmd 1

Status: Success (0x00)

Handle: 14 Address: 00:1B:DC:F2:24:10 (Vencer Co., Ltd.)

Key size: 7

> ACL Data RX: Handle 14 flags 0x02 dlen 12

L2CAP: Connection Request (0x02) ident 1 len 4

PSM: 4097 (0x1001)

Source CID: 64

< ACL Data TX: Handle 14 flags 0x00 dlen 16

L2CAP: Connection Response (0x03) ident 1 len 8

Destination CID: 64

Source CID: 64

Result: Connection successful (0x0000)

Status: No further information available (0x0000)