CVE-2026-18748 zephyrproject CVE debrief

Who should care

Defenders responsible for systems with Bluetooth Classic A2DP functionality, particularly those using Zephyr versions prior to 4.4.2, should assess exposure and prioritize patching.

Why it matters

CVE-2026-18748 is a low-severity vulnerability in Zephyr's Bluetooth Classic A2DP codec information element handling. While exploitation requires a paired BR/EDR peer, defenders should prioritize patching and monitoring due to potential information disclosure and denial of service risks.

• Potential information disclosure through out-of-bounds memory reads
• Possible denial of service through malformed AVDTP requests
• Need for verification of affected versions and patch application
• Importance of monitoring system logs for exploitation attempts

Technical summary

The Bluetooth Classic A2DP host stores a codec Information Element (IE) in struct bt_a2dp_codec_ie. When an AVDTP peer sends a codec IE longer than 8 bytes, the length is not properly validated, leading to an out-of-bounds read when the configuration is requested back. This occurs because the length is assigned from the attacker-chosen value, and later consumers trust this length. The out-of-bounds read can lead to the transmission of adjacent memory contents in response to a GET_CONFIGURATION request. The vulnerability is caused by the improper validation of codec Information Element lengths in the Bluetooth Classic A2DP host.

Defensive priority

Defenders should prioritize verifying and applying patches for affected Zephyr versions, particularly for systems with Bluetooth Classic A2DP functionality.

Recommended defensive actions

• Verify and apply patches for affected Zephyr versions
• Review and update system configurations for Bluetooth Classic A2DP functionality
• Monitor system logs for potential exploitation attempts
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up
• Review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance
• Plan vendor-supported updates or mitigations through normal change control where exposure is confirmed
• Check relevant monitoring, detection, and logs for exposed assets that need extra review

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description, affected versions, and references to patches and advisories. The vulnerability is caused by the improper validation of codec Information Element lengths in the Bluetooth Classic A2DP host. This leads to an out-of-bounds read when the configuration is requested back. The CVE record and source item also provide references to patches and advisories for affected Zephyr versions.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.