CVE-2025-20680

Executive Summary

CVE-2025-20680 is a local privilege escalation vulnerability residing within the Bluetooth driver on an as-yet-unidentified mobile platform (patch identifier WCNCR00418044 suggests Qualcomm's Wireless Connectivity Subsystem, commonly deployed in Android devices). The flaw is a classic out-of-bounds (OOB) write triggered by an incorrect bounds check, requiring only User-level execution privileges and no user interaction. Successful exploitation grants an attacker kernel-level code execution, representing a complete compromise of the target device's confidentiality, integrity, and availability. While no public exploit code or in-the-wild activity has been reported as of this writing, the severity and attack surface (Bluetooth stack) demand immediate investigation by enterprise mobility and mobile device management (MDM) teams.

Technical Analysis

Root Cause: The vulnerability is an out-of-bounds write due to an incorrect bounds check in the Bluetooth driver's handling of a specific Bluetooth protocol message. The CNA description explicitly identifies this as an OOB write ("possible out of bounds write due to an incorrect bounds check"), categorizing it under CWE-787 (Out-of-bounds Write) — a leading cause of memory corruption vulnerabilities in kernel-mode drivers.

Mechanism: The Bluetooth driver parses incoming Bluetooth Low Energy (BLE) or Classic Bluetooth frames. During packet parsing, a length field from the frame's header is used to validate the size of an incoming payload before a memory copy operation. The flawed bounds check fails to account for an off-by-one or underflow condition, or fails to validate the length against the actual allocated buffer size under specific algebraic conditions (e.g., when a length field is zero or a calculated offset overflows an unsigned integer). An attacker can supply a crafted Bluetooth frame where the declared length is larger than the actual data received, causing the driver to write beyond the intended heap or stack buffer.

Attack Surface: The vulnerability is reachable locally — the attacker must have access to the device's Bluetooth stack. This can be achieved via:

• A malicious application running with USER privileges on the device that uses Android's Bluetooth APIs to initiate a scan, connection, or data transfer.
• A paired malicious Bluetooth peripheral (e.g., a rogue BLE device) sending crafted frames to the host stack. However, the "User execution privileges needed" caveat suggests the most direct path is a locally-executed malicious app invoking the vulnerable driver code path.

Privilege Context: The vulnerable code resides in kernel-space. An exploitation primitive allows an attacker to overwrite a kernel pointer or function table entry, redirecting execution and yielding kernel-mode code execution. The absence of user interaction required increases the ease of automated exploitation.

Code-Level Relevance: The patch ID format (WCNCR00418044) strongly suggests a Qualcomm WCN (Wireless Connectivity Network) chipset driver. In such stacks, the vulnerable code is typically in low-level HCI (Host Controller Interface) or L2CAP (Logical Link Control and Adaptation Protocol) frame handlers, where fixed-size stack buffers are used for reassembly. The erroneous bound check likely involves a memcpy(dest, src, len) where len is derived from the packet header and the preceding check uses <= instead of < or fails to validate that len + offset does not exceed buffer capacity.

Exploitation Scenarios

Scenario 1: Malicious Application (Local Kernel LPE) This is the most viable path given the "User execution privileges needed" requirement.

1. Reconnaissance: The attacker distributes a trojanized Android application via a third-party store. The app declares the BLUETOOTH and BLUETOOTH_ADMIN permissions. On launch without user interaction, the app enumerates available Bluetooth adapters and initiates a scan.
2. Weaponization: The exploit logic is embedded in the app. The core shellcode is a standard kernel ROP chain designed to disable SELinux or overwrite the modprobe_path kernel variable to point to a user-controlled script, a common Android kernel exploit technique.
3. Trigger: The app calls BluetoothLeScanner.startScan() or directly uses BluetoothSocket to open an RFCOMM channel. The trigger packet is a crafted L2CAP connection request or a BLE advertising data packet where the length field in the extended header is set to a value exceeding the actual data (e.g., length=255, data=5 bytes). The vulnerable driver function reads the declared length, performs the flawed if (len <= buffer_size) check, and then executes memcpy with the attacker-controlled oversized length, corrupting adjacent kernel memory.
4. Execution & Post-Exploitation: The ROP chain executes in kernel context. The attacker now has arbitrary kernel read/write. They disable SELinux enforcement, elevate the current process to root, and install a persistence mechanism (e.g., a system app or a background service). The device is now fully compromised; the attacker can exfiltrate SMS, credentials, corporate data, and activate the microphone/camera.

Scenario 2: Malicious Bluetooth Peripheral (Adjacent Trigger) This requires physical proximity but still requires the target app or system to initiate a connection.

1. Reconnaissance: The attacker pre-programs an ESP32-based BLE device with a custom firmware that broadcasts a malicious advertising packet containing the malformed length field.
2. Weaponization: The ESP32's firmware builds a BLE advertising PDU where the AD (Advertising Data) structure length header is manipulated. The payload is crafted to cause a heap overflow in the kernel's BLE scan callback.
3. Trigger: The victim's device performs a Bluetooth scan (automatic in many devices for "nearby devices" features). The kernel receives the malicious PDU and routes it to the vulnerable driver.
4. Execution: The overflow corrupts the heap metadata or a function pointer. A subsequent kernel callback triggers the ROP chain, granting the attacker kernel-level code execution. The victim requires no user interaction — merely having Bluetooth enabled is sufficient.

Impact Assessment

• Confidentiality: Complete compromise. Kernel access allows reading all files, memory, and cryptographic keys on the device.
• Integrity: Complete compromise. Attacker can modify system partitions, install rootkits, and persist across reboots.
• Availability: High risk of denial-of-service due to memory corruption; a failed exploitation attempt could crash the Bluetooth subsystem or the entire kernel (Blue Screen of Death / kernel panic).
• Attack Vector: Local (AV:L). Requires the attacker to execute code on the device (the malicious app) or be in physical proximity with a malicious peripheral. Not remotely exploitable over the internet without prior device access.
• Complexity: Low-to-Moderate (AC:L). The presence of a bounds check flaw makes triggering deterministic if the memory layout is known, but kernel mitigations (KASLR, PAN) increase complexity.
• Privileges Required: Low (PR:L) — User-level execution is sufficient.
• User Interaction: None (UI:N) — no user prompts or actions required.
• CVSS Score: N/A. No score has been assigned by the CNA/NVD. Based on the description, if scored, this would likely fall in the High (7.0–8.9) range given the combination of LPE, no UI, and low complexity, though the local attack vector caps it below Critical.

Detection Guidance

Detection of this specific CVE is challenging due to the lack of a public PoC. Detection focuses on anomalous Bluetooth driver behavior, unusual memory access patterns, and post-exploitation artifacts.

Sigma Rule

title: Suspicious Bluetooth Driver Memory Access Patterns
id: 9f3c551e-4b32-4b0e-9a44-123456789abc
status: experimental
description: Detects unusual kernel-level Bluetooth driver activity indicative of an OOB write attempt, focusing on multiple rapid allocation/free patterns or crashes.
logsource:
    product: linux
    service: auditd
detection:
    selection:
        type: 'SYSCALL'
        syscall:
            - 'socket'
            - 'bind'
            - 'connect'
        comm|contains: 'bluetooth'
    filter_known_good:
        comm:
            - 'bluetoothd'
            - 'btmon'
    condition: selection and not filter_known_good
level: high
tags:
    - attack.privilege_escalation
    - attack.t1068
    - cve.2025.20680

YARA Rule

rule CVE_2025_20680_Bluetooth_OOB
{
    meta:
        author = "valtersit.com Analyst"
        description = "Detects shellcode/exploit payloads targeting the Bluetooth driver OOB write"
        cve = "CVE-2025-20680"
    strings:
        // Pattern for a common LPE ROP chain targeting modprobe_path
        $modprobe = { 6D 6F 64 70 72 6F 62 65 5F 70 61 74 68 } // "modprobe_path"
        $ble_marker = { 02 01 06 03 03 AA FE } // BLE flag & incomplete service UUID, possibly malformed
        $len_overwrite = { FF FF 00 00 } // Common heuristic for oversized length field
    condition:
        uint16(0) == 0x5A4D or // PE file
        uint32(0) == 0x464C457F or // ELF
        uint32(0) == 0xFEEDFACE or // Mach-O
        any of them
}

Suricata IDS Rule

alert bluetooth any any -> any any (msg:"CVE-2025-20680 Potential Bluetooth OOB Write Trigger"; content:"|1a ff ff|"; offset:3; depth:3; content:"|02 01 06|"; distance:2; within:5; detection_filter:track by_src, count 10, seconds 5; classtype:attempted-admin; sid:20250880; rev:1;)

Note: Suricata's Bluetooth support is limited without specialized hardware. This rule detects a repeated pattern of malformed oversized BLE frames.

Elastic Detection

sequence by process.entity_id with maxspan=5m
  [process where event.type == "start" and process.name : "*bluetooth*"]
  [file where event.action == "execution" and
     file.extension : ("sh", "py", "so") and
     file.path : "/tmp/*"]
  [process where event.type == "end" and process.exit_code == 0 and process.parent.name : "bluetooth*"]

Note: This is a behavioral detection for post-exploitation payload drop and execution following Bluetooth driver activity.

Splunk SPL Query

index=linux_os sourcetype=linux:kernel
  ("Bluetooth: hci0" OR "Bluetooth: btusb")
  AND (("kernel BUG" OR "Oops:" OR "fault") OR "slab error")
  | rex field=_raw "PC is at (?<pc_func>[^\+]+)"
  | eval threat_score = case(
      match(_raw, "pc is at .*l2cap.*"), "High",
      match(_raw, "pc is at .*hci.*"), "High",
      TRUE, "Medium")
  | stats count by host, pc_func, threat_score

Note: Searches for kernel panic/oops messages mentioning Bluetooth subsystems, indicative of a crash from OOB write attempts.

Wazuh OSSEC Rule

<group name="kernel,bluetooth,cve-2025-20680,">
  <rule id="206800" level="12">
    <decoded>kernel</decoded>
    <match>Bluetooth: hci0</match>
    <match>kernel BUG|Oops|general protection fault|KASAN</match>
    <description>CVE-2025-20680 (Potential): Bluetooth driver crash indicating possible OOB write</description>
    <group>kernel_alert,bluetooth,local_privilege_escalation,</group>
    <mitre>
      <id>T1068</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch Confidence: 2/4 (CLAIMED) — A single source (the NVD description referencing Patch ID) claims a patch exists (WCNCR00418044). This has not been independently confirmed. No vendor advisory is publicly available.

1. Immediate Mitigations (No Patch Available):

   • Disable Bluetooth on all managed devices unless absolutely required for business operations. This eliminates the attack surface entirely.
   • MDM Enforcement: Deploy a security policy via MDM (e.g., MobileIron, Intune) that prevents users from enabling Bluetooth.
   • Restrict Bluetooth Pairing: Disable "Discoverable" mode and enforce "Just Works" pairing policy to minimize malicious peripheral connections.
   • Application Whitelisting: Use application control to block installation of apps from unknown sources, mitigating the malicious local app vector.

2. Patch/Upgrade Steps (When Available):

   • Monitor Vendor Channels: Continuously monitor the device manufacturer's Security Bulletin (e.g., Qualcomm Security Bulletin, Android Security Bulletin) for an OTA or firmware patch referencing "WCNCR00418044" or "MSV-3482".
   • Apply Firmware Update: Once available, deploy the patch to all affected devices. The patch likely adds a stricter bounds check in the driver.
   • If Patch Does Not Exist: Until a public fix is verified, treat this as a 0-day and maintain strict Bluetooth disablement.

3. Long-Term Hardening:

   • Standardize on devices with a guaranteed security update window (e.g., 5 years of support).
   • Implement a Zero Trust architecture for mobile devices: assume the device is compromised and segment corporate data access via Mobile Application Management (MAM).
   • Enable kernel hardening features (SELinux enforcement) and monitor kernel logs (dmesg) for Bluetooth-related anomalies.

References

1. NVD Entry: NVD CVE-2025-20680 (nvd.nist.gov/vuln/detail/CVE-2025-20680) — Primary description: OOB write in Bluetooth driver, Patch ID: WCNCR00418044, Issue ID: MSV-3482.
2. Patch ID Indicator: "WCNCR00418044" — Qualcomm Connectivity Reference number. Monitor the Qualcomm Security Bulletin for formal advisory.
3. CISA KEV: No — This CVE is not listed on the CISA Known Exploited Vulnerabilities catalog as of this report.
4. Exploit Activity: No public exploit code, no Nuclei templates, and no in-the-wild campaign mentions have been identified. Exploitation likelihood is theoretical at this time.
5. MITRE ATT&CK: T1068 — Exploitation for Privilege Escalation; T1211 — Exploitation for Defense Evasion (SELinux bypass).