CVE-2026-12236
Received Received - Intake

Bluetooth Host GATT Client Infinite Loop Vulnerability

Publication date: 2026-08-13

Last updated on: 2026-08-13

Assigner: Zephyr Project

Description
The Bluetooth host GATT client function parse_read_std_char_desc() in subsys/bluetooth/host/gatt.c parses an ATT Read By Type Response received from a remote GATT server during BT_GATT_DISCOVER_STD_CHAR_DESC discovery. The per-entry stride rsp->len is taken directly from the peer's PDU, and the parse loop both tests its exit condition (length >= rsp->len) and advances (length -= rsp->len, pdu += rsp->len) using that value. The minimum value of rsp->len was never validated before the loop. A malicious or malfunctioning peer can reply with rsp->len = 0. Because length is unsigned and never decreases, the loop condition stays true forever and the read pointer never advances; as long as the body is at least a few bytes with a non-zero handle and a matching descriptor UUID, the host repeatedly re-parses the same bytes and invokes the discovery callback, never terminating. This hangs the Bluetooth host processing thread (CWE-835, loop with unreachable exit condition). The condition is reachable by any connected peer once the local device initiates standard-descriptor-value discovery; GATT discovery does not require bonding or encryption, so an unauthenticated adjacent attacker that the device connects to can trigger it. The impact is denial of service of the Bluetooth subsystem (and likely a watchdog reset on constrained targets); there is no memory disclosure or corruption. The fix adds a rsp->len < sizeof(struct bt_att_data) check before the loop, rejecting under-length responses so the stride is always non-zero and the loop terminates. The sibling parsers parse_include() and parse_characteristic() already validated rsp->len and are unaffected.

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Meta Information

Published
2026-08-13
Last Modified
2026-08-13
Generated
2026-08-13
AI Q&A
2026-08-13
EPSS Evaluated
N/A
NVD
CVE-2026-12236
EUVD
EUVD-2026-58131

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
zephyrproject zephyr From 2.6.0 (inc) to 4.4.0 (inc)
zephyrproject zephyr *

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-835 The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

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Executive Summary

This is a denial-of-service vulnerability in the Zephyr RTOS Bluetooth GATT client. It occurs in the parse_read_std_char_desc() function where an infinite loop happens if a peer sends a response with zero data length. The loop condition depends on an unvalidated rsp->len value, causing the thread to hang indefinitely.

Detection Guidance

Detecting this vulnerability requires monitoring for abnormal Bluetooth host thread behavior or infinite loops during GATT discovery. Check for unresponsive Bluetooth processes or watchdog resets on constrained devices. Use system logs to identify Bluetooth subsystem hangs during standard-descriptor discovery.

Impact Analysis

The vulnerability can cause the Bluetooth host processing thread to hang, leading to a denial-of-service condition. On constrained devices, this may trigger a watchdog reset. The impact is limited to service disruption as there is no memory disclosure or corruption.

Mitigation Strategies
  • Update Zephyr RTOS to a patched version (v4.4.0 or later, or backported fixes for v4.3/v3.7).
  • Apply the official patch from the Zephyr project commit 494283d469a95b294badaf45c639de433bf5e35a.
  • Restrict Bluetooth connections to trusted devices until patched.

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