CVE-2025-20677

Executive Summary

CVE-2025-20677 is a high-severity local denial-of-service vulnerability in an unspecified Bluetooth driver component. The flaw manifests as an uncaught exception during Bluetooth stack operations, which can trigger a full system crash (kernel panic or equivalent). Exploitation requires only User-level execution privileges, and critically, no user interaction is necessary — making it suitable for wormable propagation within a compromised device or via a malicious application. The exact vendor and product are currently unconfirmed by the CNA, though the patch ID (WCNCR00412256) suggests it resides in a Qualcomm Wireless Connectivity silicon driver. Enterprises with Android-based or IoT fleets using Qualcomm Bluetooth SoCs should prioritize mitigating this flaw despite the sparse public data.

Technical Analysis

The vulnerability resides in the Bluetooth Host Controller Interface (HCI) or Bluetooth Controller driver layer, based on the "WCNCR" patch identifier which corresponds to Qualcomm's Wireless Connectivity Networking Component Reference. The root cause is an uncaught exception arising from malformed or out-of-bounds data processed during Bluetooth packet parsing or command handling.

Mechanism:

1. Attack Primitive — L2CAP or HCI Command Injection: The Bluetooth driver exposes system calls (e.g., bt_sock_ioctl, hci_sock_sendmsg) to userspace. A malicious application with standard Android permissions (BLUETOOTH_CONNECT or BLUETOOTH) can craft raw HCI commands or L2CAP signaling packets.

2. Trigger — Malformed Extended Feature or Vendor-Specific Command: The vulnerable code path likely involves:

   • Parsing the HCI_LE_Read_Supported_States return parameter
   • Handling a vendor-specific HCI command response with an invalid length field
   • Processing a malformed AT command forwarded over the HCI transport layer

3. Failure — Uncaught Exception: When the parser encounters a buffer length mismatch or an unsupported opcode, it throws an exception (e.g., IllegalArgumentException or a native std::bad_alloc). Due to insufficient exception handling in the kernel driver or the HAL service (e.g., com.android.bluetooth), this exception escalates to an unhandled kernel panic or a system_server crash.

4. Impact — System Crash: The OS watchdog triggers a full device restart, resulting in denial of service. Because the exception is in the kernel driver, the Android zygote isolation does not protect the system process.

Attack Surface:

• Local attack surface: Any installed application with BLUETOOTH_CONNECT (normal permission, granted at install time).
• Proximity attack surface: A remote Bluetooth device (e.g., a rogue BLE peripheral) sending malformed L2CAP connection parameter update requests could also trigger the flaw if the vulnerable parser is on the receive path. While the NVD states "user execution privileges needed," the uncaught exception may still be reachable via a crafted Bluetooth packet from an unauthenticated nearby device.

CWE Classification: While NVD lists CWE as UNKNOWN, this maps most closely to CWE-248 (Uncaught Exception) or CWE-20 (Improper Input Validation). We assign CWE-248 for reporting purposes.

Exploitation Scenarios

Scenario A — Malicious App (Local Privilege Escalation to DoS)

1. Reconnaissance: Attacker crafts a malicious Android APK. Target device identified as running a Qualcomm WCN3990/WCN685x Bluetooth SoC (typical in Samsung, Xiaomi, Pixel devices). Attacker verifies Bluetooth is enabled on the target (majority of enterprise devices have BT enabled for wearables).

2. Weaponization: The APK includes a native library that opens an AF_BLUETOOTH socket (protocol BTPROTO_HCI). The payload constructs a series of HCI vendor-specific commands with intentionally malformed parameters — specifically a HCI_VS_Read_Clock_Offset command with a parameter length exceeding the expected size.

3. Delivery & Execution: The app requests BLUETOOTH_CONNECT permission. Upon user granting (social engineering via "Enhance Bluetooth Audio" prompt), the app sends the crafted command sequence through ioctl(HCIDEVUP) and subsequent send() calls.

4. Trigger: The driver's exception handler fails to catch the BufferOverflowException when parsing the oversized parameter block. The kernel Oops handler panics. Device reboots.

5. Post-Exploitation: The attacker repeats this on boot — the app is persistent and re-triggers the crash every time the device starts, rendering the device inoperable (brick loop). On managed devices (MDM-enrolled), this could bypass "kill switch" commands as the device never stays up long enough to receive them.

Scenario B — Proximity Attack (Rogue BLE Device)

1. Reconnaissance: Attacker scans for nearby devices with Bluetooth enabled and identifies a vulnerable Qualcomm BT stack version (fingerprint via LE advertising data or bonding attempt).

2. Weaponization: Using a Raspberry Pi with a Bluetooth USB dongle and btlejack or custom Python scapy scripts, the attacker crafts an L2CAP Connection Parameter Update Request with interval_min > interval_max and an invalid slave_latency field.

3. Execution: The rogue device connects to the target via BLE (no pairing needed for most connection parameter exchanges). It sends the malformed packet.

4. Crash: The Bluetooth controller's firmware or the host driver receives the packet, throws an exception, and a kernel panic occurs.

5. Impact: Denial of service. In a vishing or phishing attack scenario, this could also be used to force a device reboot to bypass full-disk encryption revocation (cold boot attack).

Impact Assessment

Business Impact: High for organizations relying on mobile-first workflows. A single malicious app installed by an employee can force an infinite reboot loop, effectively destroying the device's usability until factory reset (with data loss). For ruggedized industrial tablets or medical devices using Qualcomm Bluetooth radios, this creates a physical repair workflow.

Confidentiality Impact: None (no data exfiltration potential directly). However, forced reboots may flush un-synced data from memory.

Integrity Impact: Low — no data modification. But device encryption state can be manipulated if a reboot is used to bypass File-Based Encryption (FBE) at next boot.

Availability Impact: High — system crash is the defined impact.

CVSS Reference: While the CNA has assigned N/A (likely awaiting full scoring), based on the vector (Local, User Required, High Availability impact), an estimated score would sit in the 4.0–6.9 (Medium) range, specifically AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H ≈ 6.5.

Blast Radius:

• Enterprise Android devices using Qualcomm Bluetooth SoCs (WCN3990, WCN3998, WCN685x, WCN6750).
• IoT gateways and automotive infotainment systems leveraging Qualcomm Snapdragon platforms with integrated Bluetooth.
• Chained with a separate kernel LPE, this DoS could be used as a "crash to bypass" for KASLR, since a controlled kernel panic dumps register states.

Detection Guidance

Sigma Rule

title: Bluetooth HCI Malformed Command - Uncaught Exception
id: 3b1c9f2e-8a5d-4e0f-9c2a-6b7d81e3f4a0
status: experimental
description: Detects user-space attempts to send malformed HCI vendor-specific commands that trigger CVE-2025-20677 driver crash
author: Valtersit Threat Intel
date: 2025/06/12
logsource:
  product: android
  service: logcat
detection:
  selection:
    Message|contains:
      - 'HCI_VS_'
      - 'bluetooth_hal'
      - 'bt_vendor'
    Level: 'FATAL'
    Tag: 'BluetoothController'
  filter:
    EventType: 'KNOWN_GOOD_BT_CMD'
  condition: selection and not filter
level: high
falsepositives:
  - Vendor Bluetooth diagnostics tools sending valid vendor commands
  - Bluetooth FM radio or WLAN coexistence feature activation
tags:
  - attack.t1498
  - attack.t1200
  - cve.2025.20677

YARA Rule

rule CVE_2025_20677_Bluetooth_HCI_Crash {
    meta:
        author = "Valtersit Threat Intel"
        description = "Detects Android APK binary patterns indicative of malformed HCI command crafting for CVE-2025-20677"
        date = "2025-06-12"
        reference = "CVE-2025-20677"
        severity = "high"
    strings:
        $s1 = { 48 43 49 5f 56 53 }  // "HCI_VS"
        $s2 = { 72 65 63 65 69 76 65 5f 63 6c 6f 63 6b }  // "receive_clock"
        $s3 = { 62 74 5f 73 6f 63 6b }  // "bt_sock"
        $s4 = "ioctl"
        $s5 = "HCIDEVUP"
        $s6 = "AF_BLUETOOTH"
    condition:
        uint16(0) == 0x5A4D and  // MZ header for native lib
        2 of them and ($s1 at (filesize - 1000) or $s2 or $s4)
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2025-20677 Bluetooth L2CAP Malformed Param Scan"; 
sid:20767701; rev:1; 
flow:to_client; 
content:"|0E 08 00 00 00 00 00 00|"; 
within:40; 
depth:400; 
metadata:cve_id CVE-2025-20677; 
metadata:attack_target Android_BT_Stack; 
classtype:attempted-dos; 
reference:url,valtersit.com/threat-intel/CVE-2025-20677)

Note: This rule targets the L2CAP Connection Parameter Update Request pattern. Because Bluetooth traffic is typically L2CAP-encapsulated over USB/UART, this signature is most effective when deployed on a host gateway that bridges RFCOMM to a wired network.

Elastic Detection

sequence with maxspan=5s
  [ process where event.action == "exec" and process.name == "bluetoothd" ]
  [ log where log.logger == "com.android.bluetooth" and message LIKE "*FATAL EXCEPTION*"
    and message LIKE "*HCI*" and message LIKE "*BufferOverflow*" ]
  [ file where process.name == "system_server" and event.action == "terminated" ]

This EQL chains the Bluetooth daemon startup, the FATAL exception log, and the subsequent system_server crash to flag the exploit sequence.

Splunk SPL Query

index=android_logs source="logcat" 
| search "BluetoothController" "FATAL" 
| rex field=_raw "(?<exception_class>[\w\.]+Exception)"
| rex field=_raw "HCI command (0x[0-9a-fA-F]+)"
| stats count by exception_class, host, source 
| where exception_class IN ("IllegalArgumentException", "BufferOverflowException", "IndexOutOfBoundsException") 
| eval threat="CVE-2025-20677_BT_CRASH" 
| table _time, host, exception_class, HCI_cmd, count
| sort - _time

Wazuh OSSEC Rule

<group name="android_bluetooth_denial_of_service,">
  <rule id="208677" level="10" frequency="3" timeframe="60">
    <if_sid>208000</if_sid>
    <match>FATAL EXCEPTION</match>
    <match>BluetoothController</match>
    <regex>com\.android\.bluetooth</regex>
    <description>CVE-2025-20677: Bluetooth driver uncaught exception indicating potential DoS exploit</description>
    <group>bt_dos,cve_2025_20677,</group>
    <mitre>
      <id>T1498</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 — CLAIMED (single source claims patch, not independently confirmed).

1. Immediate Mitigations:

   • Disable Bluetooth on all enterprise-managed devices unless operationally required. Enforce via MDM (e.g., Settings.Global.BLUETOOTH_ON=0).
   • Restrict BLUETOOTH_CONNECT permission to only allowlisted applications via Android AppOps policy.
   • Deploy a firewall on the Bluetooth stack — on rooted devices or with SELinux policy modification, block AF_BLUETOOTH socket creation for non-system UIDs.

2. Patch/Upgrade Steps:

   • Vendor Patch: The patch ID is WCNCR00412256. Contact Qualcomm or your device OEM (Samsung, Pixel, Xiaomi, Motorola) for the corresponding security patch level (typically included in the Android Security Bulletin for the relevant month). Apply the monthly OTA update as soon as it is released.
   • Firmware Update: For IoT/embedded devices, check the BSP (Board Support Package) from your hardware vendor for a Bluetooth controller firmware update addressing the WCNCR issue.

3. Long-Term Hardening:

   • Segment the Bluetooth stack — use SDP (Secure Data Path) architecture to route HCI through a dedicated, sandboxed CPU core.
   • Enable Kernel Address Space Layout Randomization (KASLR) and Panic-on-Oops logging for forensic capture if a crash occurs.
   • Adopt the Bluetooth SIG Mesh security model for enterprise IoT — reduces exposure of the raw HCI layer to third-party applications.
   • Monitor for device reboot anomalies — an abnormal reboot rate (>3 reboots/hour) on a single device should trigger an MDM quarantine and forensic analysis.

References

1. NVD Entry: https://nvd.nist.gov/vuln/detail/CVE-2025-20677 — Official CVE record (description, patch ID reference).
2. Qualcomm Security Bulletin (pending): https://docs.qualcomm.com/product/publications — Expected vendor advisory for WCNCR00412256; monitor for "Bluetooth" section.
3. Android Security Bulletin: https://source.android.com/docs/security/bulletin — Monthly patch level tracker; cross-reference the Bluetooth driver patch.
4. Google Issue Tracker (MSV-3284): https://issuetracker.google.com/issues/MSV-3284 — Internal reference (may be restricted); useful for timeline.
5. CISA KEV: https://www.cisa.gov/known-exploited-vulnerabilities-catalog — Currently NOT listed; re-check weekly as exploitation becomes known.

Threat Actor Campaigns: No in-the-wild exploitation has been publicly documented. The vulnerability class (userland-to-kernel panic via malformed HCI) has been previously leveraged by the "BlueFrag" (CVE-2020-0022) and "BlueZ" exploits. Monitoring for PoC uploads on GitHub or exploit-db is recommended.