CVE-2026-14297: Bluetooth CGMS Buffer Overflow Vulnerability

CVE-2026-14297 Overview

CVE-2026-14297 is a buffer overflow vulnerability in the Bluetooth Continuous Glucose Monitoring Service (CGMS) Record Access Control Point (RACP) write handler. An authenticated Bluetooth Low Energy (BLE) peer can overflow a 20-byte static buffer and corrupt adjacent BSS memory. The flaw is tracked under CWE-787: Out-of-Bounds Write and affects firmware built on Nordic Semiconductor's BLE stack components. The exploitable outcome depends on the linker-assigned BSS layout of each firmware build, making impact vary across devices.

Critical Impact
An adjacent-network attacker paired with the target device can corrupt memory adjacent to the 20-byte CGMS buffer, potentially altering firmware state, causing denial of service, or enabling code execution depending on the build layout.

Affected Products

Firmware implementing the Bluetooth CGMS profile with the vulnerable RACP write handler
Nordic Semiconductor BLE stack components referenced in the Nordic Semiconductor Documentation
Continuous glucose monitoring devices and BLE peripherals reusing the CGMS reference implementation

Discovery Timeline

2026-09-07 - CVE-2026-14297 published to NVD
2026-09-09 - Last updated in NVD database

Technical Details for CVE-2026-14297

Vulnerability Analysis

The vulnerability resides in the RACP write handler exposed by the CGMS GATT service. RACP allows a connected BLE client to request stored glucose measurement records using structured operands. The handler copies attacker-controlled bytes from the GATT write payload into a fixed 20-byte static buffer without validating the incoming length.

Because the buffer is stored in the BSS segment, an overflow does not corrupt a stack canary or return address. Instead, adjacent global variables and static state used by the BLE stack are overwritten. The specific variables clobbered depend on how the linker orders symbols in the compiled firmware image.

This layout dependency means one firmware build may only suffer a crash while another may allow control of stack pointers, function pointers, or connection state. Attackers who profile a target build can craft deterministic corruption chains.

Root Cause

The RACP write callback trusts the attribute write length supplied by the peer. It uses a static 20-byte destination sized for the maximum expected RACP operation but performs no bounds check before copying. Any bonded or authenticated peer can issue a write larger than the buffer.

Attack Vector

Exploitation requires BLE adjacency and successful pairing or bonding with the target, matching the CVSS 4.0 vector AV:A/AC:L/PR:N. The attacker connects to the CGMS service, subscribes to RACP indications, and issues a write to the RACP characteristic with a payload exceeding 20 bytes. The overflow then corrupts BSS state used by the BLE stack or application logic.

No public proof-of-concept is available. The EPSS forecast places near-term exploitation probability low, but the physical accessibility of BLE medical devices raises the risk in targeted scenarios.

Detection Methods for CVE-2026-14297

Indicators of Compromise

BLE GATT writes to the RACP characteristic (UUID 0x2A52) with attribute value length greater than 20 bytes
Unexpected firmware resets, watchdog timeouts, or hard faults following BLE client interaction with the CGMS service
BLE peers issuing malformed RACP opcodes or operands inconsistent with the CGMS specification

Detection Strategies

Instrument the RACP write callback to log any attribute write where the length exceeds the expected operand size
Capture BLE sniffer traces during device pairing and inspect RACP transactions for oversized payloads
Correlate firmware crash telemetry with BLE connection events from the same peer identity

Monitoring Recommendations

Track fault logs and coredumps from deployed devices for anomalies aligned to CGMS handler frames
Monitor bonded-device lists for unexpected additions that could stage adjacent-network access
Review vendor advisories from Nordic Semiconductor and downstream device manufacturers for firmware updates

How to Mitigate CVE-2026-14297

Immediate Actions Required

Inventory BLE devices exposing the CGMS profile and identify their firmware build and stack version
Restrict pairing to trusted clients and disable open bonding where operationally feasible
Apply vendor firmware updates once released by Nordic Semiconductor or the downstream device manufacturer

Patch Information

No specific patch identifier is listed in the NVD entry at the time of publication. Consult the Nordic Semiconductor Documentation and device manufacturer advisories for corrected firmware releases. The fix requires enforcing a length check in the RACP write handler and clamping copies to the 20-byte buffer size.

Workarounds

Disable the CGMS service on devices where continuous glucose monitoring is not required
Reduce BLE transmit power and limit advertising windows to shrink the adjacent-network exposure
Enforce BLE Security Mode 1 Level 4 (LE Secure Connections with authenticated pairing) to raise the barrier to authenticated access

bash

# Configuration example: enforce length validation in the RACP write handler
# (illustrative pseudocode reflecting the required fix)
if (write_len > sizeof(racp_buffer)) {
    return BLE_GATT_ERR_INVALID_ATTR_VALUE_LENGTH;
}
memcpy(racp_buffer, write_data, write_len);