CVE-2026-53254: Linux Kernel Bluetooth RFCOMM Out-of-Bounds Read Vulnerability

Technical summary

CVE-2026-53254 is an out-of-bounds read vulnerability (CWE-125) in the Linux kernel's Bluetooth RFCOMM MCC (Mobile Control Command) handler. The vulnerability exists because MCC handlers cast skb->data pointers directly to protocol-specific structures without first validating that skb->len contains sufficient bytes. A remote Bluetooth device can send truncated MCC frames that trigger out-of-bounds memory access during struct dereferencing. The fix employs skb_pull_data() to validate frame length and safely extract data. Special handling is required for rfcomm_recv_rpn() to comply with ETSI TS 07.10, which permits 1-byte RPN requests; the patch validates the DLCI byte first, then validates the full struct only when frame length exceeds 1 byte.

Business impact

This vulnerability poses a confidentiality and availability risk to systems running vulnerable Linux kernels with Bluetooth enabled. An attacker within Bluetooth range can trigger memory disclosure or kernel crashes without credentials. In environments where Bluetooth is exposed (embedded IoT devices, laptops in shared spaces, automotive systems), this could lead to leakage of sensitive kernel memory or denial of service. Organizations relying on Bluetooth-enabled Linux devices should prioritize patching to prevent information disclosure and system instability.

Affected systems

The Linux kernel is affected across multiple versions. Vulnerable systems include any Linux installation with Bluetooth RFCOMM support enabled. This includes desktop and laptop systems with Bluetooth radios, embedded Linux devices, IoT appliances, and automotive systems using Linux-based infotainment platforms. The vulnerability requires Bluetooth to be present and accessible; systems with Bluetooth disabled or physically removed are not at risk.

Exploitability

The vulnerability is exploitable with low complexity. An attacker must be within Bluetooth range (typically 10–100 meters depending on hardware) and does not require authentication or user interaction. The attack vector is adjacent network (Bluetooth), and no special privileges are needed. Exploitation involves crafting and sending malformed RFCOMM frames, which can be done using publicly available Bluetooth protocol tools. Active exploitation is straightforward, making this a practical threat in environments where untrusted Bluetooth devices may connect.

Remediation

Remediation requires applying a Linux kernel patch that implements proper skb length validation in RFCOMM MCC handlers using skb_pull_data(). Users must update their kernel to a version incorporating the fix. Interim mitigations include disabling Bluetooth if not required, restricting Bluetooth visibility, enabling Bluetooth authentication/pairing requirements, and isolating Bluetooth-enabled systems from sensitive networks. Vendors shipping affected devices should release kernel updates to all supported product lines.

Patch guidance

Install a patched Linux kernel version that includes the fix for CVE-2026-53254. Consult your distribution's security advisory for specific patched kernel versions (e.g., stable, longterm, or distribution-specific backports). For enterprise deployments, verify patch availability from your Linux vendor before rolling out updates. Test patches in a non-production environment to ensure compatibility with your hardware and workloads. Kernel updates typically require a reboot; schedule updates during maintenance windows.

Detection guidance

Monitor system logs for Bluetooth-related errors or kernel warnings, particularly in dmesg or syslog entries mentioning RFCOMM, out-of-bounds access, or BUG reports. Intrusion detection systems can be configured to alert on unusual Bluetooth traffic patterns or connection attempts from unknown devices. Perform periodic audits of Bluetooth device pairings to detect unauthorized connections. Check kernel versions on vulnerable systems using 'uname -r' and cross-reference against vendor advisories. For forensic analysis, examine kernel memory dumps for evidence of memory disclosure or corruption patterns consistent with out-of-bounds reads.

Why prioritize this

With a CVSS score of 8.1 (HIGH severity), this vulnerability merits priority remediation. The combination of adjacent-network attack vector, lack of authentication requirement, and dual impact on confidentiality and availability creates significant risk. Bluetooth is increasingly prevalent in enterprise and consumer devices, expanding the attack surface. The straightforward exploitability and lack of user interaction barriers elevate practical risk. Organizations should prioritize patching systems where Bluetooth is enabled, especially on devices processing or storing sensitive data.

Risk score, explained

The CVSS 3.1 score of 8.1 reflects a high-severity vulnerability with the following components: Attack Vector (Adjacent) indicates the attacker must be physically proximate but not on the same network; Attack Complexity (Low) means no special conditions are required; Privileges Required (None) and User Interaction (None) confirm the attack requires neither authentication nor user action; Scope (Unchanged) limits impact to the vulnerable component; Confidentiality Impact (High) reflects memory disclosure capability; Integrity Impact (None) indicates the vulnerability does not allow data modification; and Availability Impact (High) reflects potential for kernel crashes. The score balances the proximity requirement against the combination of information disclosure and denial-of-service potential.

Frequently asked questions