Junglewise Threat Intelligence

CVE-2026-43134: Linux Kernel Bluetooth L2CAP missing key size check in LE connection request

CVE-2026-43134 · Severity: high · CVSS 8.1 · Published 2026-05-06

Technologies: Linux Kernel. Vendors: Linux.

Executive brief

A security vulnerability has been identified in the Linux kernel's Bluetooth component. The system fails to properly verify the size of encryption keys during certain Bluetooth connection requests. This could allow an attacker within Bluetooth range to establish a connection with insufficient security, potentially leading to unauthorized access or data interception.

Technical details

A vulnerability exists in the Linux kernel Bluetooth subsystem (net/bluetooth/l2cap_core.c) due to a missing encryption key size check when processing L2CAP_LE_CONN_REQ packets. An attacker within Bluetooth range (Adjacent) can initiate a Low Energy (LE) connection request that bypasses intended security level requirements by using an insufficient key size. The fix introduces a call to l2cap_check_enc_key_size to ensure the key meets the required security level, returning L2CAP_CR_LE_BAD_KEY_SIZE if it fails. This issue affects multiple stable kernel branches from 3.14 through 6.19.x.

Affected products

  • Linux Linux Kernel 3.14 to 5.10.252, 5.11 to 5.15.202, 5.16 to 6.1.165, 6.2 to 6.6.128, 6.7 to 6.12.75, 6.13 to 6.18.16, 6.19 to 6.19.6

Timeline

  • 2026-05-06: advisory: Initial disclosure of CVE-2026-43134
  • 2026-02-23: patched: Mainline patch committed by Luiz Augusto von Dentz

References

Related threats