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CVE-2025-39889— Bluetooth: l2cap: Check encryption key size on incoming connection

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未检查传入连接的加密密钥大小，可能导致安全模式4级别4要求的16字节密钥大小被绕过。

CVSS 8.1 · High EPSS 0.10% · P1

Possible ATT&CK Techniques 1 AI

T1072 · Software Deployment Tools

Affected Version Matrix 15

VendorProduct Version RangeStatus
Linux Linux 4f911a538e089cce808a15dc3277250f4f8daef9< ed503d340a501e414114ddc614a3aae4f6e9eae2 affected
288c06973daae4637f25a0d1bdaf65fdbf8455f9< 24b2cdfc16e9bd6ab3d03b8e01c590755bd3141f affected
288c06973daae4637f25a0d1bdaf65fdbf8455f9< c6d527bbd3d3896375079f5dbc8b7f96734a3ba5 affected
288c06973daae4637f25a0d1bdaf65fdbf8455f9< 9e3114958d87ea88383cbbf38c89e04b8ea1bce5 affected
288c06973daae4637f25a0d1bdaf65fdbf8455f9< d49798ecd26e0ee7995a7fc1e90ca5cd9b4402d6 affected
288c06973daae4637f25a0d1bdaf65fdbf8455f9< d4ca2fd218caafbf50e3343ba1260c6a23b5676a affected
288c06973daae4637f25a0d1bdaf65fdbf8455f9< 522e9ed157e3c21b4dd623c79967f72c21e45b78 affected
5.11 affected
… +7 more rows
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I. Basic Information for CVE-2025-39889

Vulnerability Information
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Vulnerability Title
Bluetooth: l2cap: Check encryption key size on incoming connection
Source: CVE Program / CVE List V5
Vulnerability Description
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)
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于未检查传入连接的加密密钥大小，可能导致安全模式4级别4要求的16字节密钥大小被绕过。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 4f911a538e089cce808a15dc3277250f4f8daef9 ~ ed503d340a501e414114ddc614a3aae4f6e9eae2 -
Linux Linux 5.11 -

II. Public POCs for CVE-2025-39889

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III. Intelligence Information for CVE-2025-39889

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Patches & Fixes for CVE-2025-39889 (1)

Same Patch Batch · Linux · 2025-09-24 · 3 CVEs total

CVE-2024-58241 7.8 HIGH Bluetooth: hci_core: Disable works on hci_unregister_dev
CVE-2025-39890 wifi: ath12k: fix memory leak in ath12k_service_ready_ext_event

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-39889

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