CVE-2026-20523

Executive Summary

CVE-2026-20523 is a high-severity out-of-bounds write (CWE-787) in the MediaTek NeuroPilot component of the MT6881 firmware platform, caused by a missing bounds check. Successful exploitation requires only local access to the device — no additional execution privileges and no user interaction — and yields full compromise of confidentiality, integrity, and availability (CVSS 3.1 base 8.4). Affected systems are devices running MT6881 firmware that expose the NeuroPilot subsystem to a local attacker context, such as a malicious or compromised application running on the host OS.

Technical Analysis

The vulnerability resides in the MediaTek NeuroPilot stack — the vendor's on-device AI/neural processing framework — as implemented in MT6881 firmware. The NVD description states that the flaw is an out-of-bounds write caused by a missing bounds check. In CWE-787 terms, this means a memory write operation reaches an index or length value that has not been validated against the size of the destination buffer, allowing data to be written past the end of the intended allocation.

Two properties of the description materially shape the risk profile:

1. Missing bounds check, not a logic-only error. The root cause is the absence of a validation step prior to a write, meaning the vulnerable code trusts an externally influenced value (for example, a size, offset, or index derived from input supplied by the caller) without clamping or rejecting it.
2. Local attack vector with no privileges and no user interaction. Per the CVSS vector (AV:L, PR:N, UI:N), the attacker already has a foothold in a local context — such as code executing on the device — but does not need elevated privileges to reach the vulnerable code path, and the victim does not need to take any action for exploitation to succeed.

Because the write primitive is out-of-bounds, an attacker who controls the offending value can corrupt adjacent memory. In a firmware/HAL-adjacent component, that corrupted memory may include control structures, object metadata, or function pointers used by the NeuroPilot service or its client processes. This is the classic precursor to arbitrary code execution or, at minimum, denial of service through memory corruption.

The NVD description does not identify the specific function, buffer, parameter, or NeuroPilot subcomponent involved. No patch diff, source code, or advisory detail describing the exact code path is available. Accordingly, the precise trigger conditions — which API call, which buffer, which index — cannot be stated with confidence and are deliberately not fabricated here. What can be stated with confidence from the description is the vulnerability class, the affected component (NeuroPilot on MT6881 firmware), the missing validation mechanism, and the resulting out-of-bounds write.

Exploitation Scenarios

No public proof-of-concept, exploit code, or Nuclei template is available for CVE-2026-20523 (EPSS 0.00133, 2.4th percentile). The attack chain below is inferred strictly from the vulnerability class and the CVSS vector; it does not rely on any invented function names, endpoints, or parameters.

1. Reconnaissance / target identification. The attacker identifies a target device running MT6881 firmware whose NeuroPilot subsystem is reachable from the attacker's current execution context. Because the vector is local (AV:L) and requires no privileges (PR:N), the attacker's starting position can be unprivileged code running on the device — for example, a malicious or trojanized application installed through normal means, or a compromised process.
2. Triggering the flaw. The attacker causes the vulnerable NeuroPilot code path to process an input that drives a write past the bounds of a target buffer. The precondition is the missing bounds check described by NVD: a value influencing the write (length, index, or offset) is not validated against the destination buffer size. The attacker only needs to supply or influence that value; no special permissions are required to invoke the path, and no user interaction occurs.
3. Payload / execution method. At the vulnerability-class level, an out-of-bounds write of attacker-influenced data enables memory corruption. Depending on the layout of the adjacent memory, the write can be shaped into overwriting control data, corrupting heap or object metadata, or placing attacker-controlled values into a region that is later consumed as a pointer or length. This is the standard progression from CWE-787 to control-flow hijack or to a controlled memory primitive. No specific gadget, function name, or offset is claimed here because none is available in the source data.
4. Post-exploitation impact. Given the scorer's assessment of High confidentiality, integrity, and availability impact (C:H/I:H/A:H), successful exploitation can expose sensitive data handled by the NeuroPilot subsystem, allow modification of data or code behavior, and disrupt the affected process or device function. Because the attacker begins without privileges (PR:N) and the vulnerability yields a memory-write primitive in a system component, the realistic outcome is local escalation of privilege on the device — moving from an unprivileged or sandboxed application context toward code execution at the privilege level of the affected NeuroPilot service.

Note: the affected version range, the fixed version, and the exact privilege boundary crossed are not disclosed in the available data; the escalation step cannot be mapped to a named kernel/user boundary without that information.

Impact Assessment

CVE-2026-20523 carries a CVSS 3.1 base score of 8.4, rated High severity, with the vector CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. The subscore composition is significant:

• AV:L (Local) — exploitation requires a local presence on the device; remote, unauthenticated network exploitation is not the intended attack path. This caps the base score but does not reduce the consequence of success.
• AC:L (Low) — no special conditions beyond a viable trigger are required; the attack is repeatable under normal operations.
• PR:N (None) — the attacker needs no prior privileges, meaning any unprivileged code execution context on the device (for example, an installed application) is sufficient as a starting point.
• UI:N (None) — no victim interaction; exploitation does not depend on the user opening a file, granting permission, or approving a prompt.
• S:U (Unchanged) — the vulnerable component's compromise does not, per the scorer, cross a scope boundary in the CVSS model; impact is assessed within the affected security authority.
• C:H/I:H/A:H — full loss of confidentiality, integrity, and availability within the affected component's scope.

Affected systems. Devices based on the MediaTek MT6881 platform and running MT6881 firmware, specifically where the NeuroPilot component is exposed to a local caller context. No affected version range was published in the available data (the "Affected Versions" field is empty), which is a material gap for asset inventory.

Blast radius. Because the vector is local and requires no privileges, the effective blast radius is any MT6881 device on which an attacker can obtain code execution in the local context that can reach NeuroPilot. This includes consumer and embedded devices built on the platform. The unpatched status (patch confidence 0/4) and absence of public exploit code together define the current risk posture: there is no evidence of in-the-wild exploitation, but the latent capability is significant and the fix readiness is unverified. No CISA KEV listing exists for this CVE.

Threat context. EPSS 0.00133 places this CVE at the 2.4th percentile of exploited vulnerabilities, indicating very low near-term exploitation likelihood as modeled at the time of scoring. No known threat actor campaigns or exploit-in-the-wild evidence are associated with this CVE. This score should be revisited if exploit code or targeted campaign reporting emerges.

Detection Guidance

The detection content below targets the general CWE-787 local memory-corruption pattern on Android/Linux-based MediaTek device platforms: process crashes in the NeuroPilot service, malformed inputs to AI/NPU processing paths, and anomalous memory-corruption telemetry. Because no specific function names, file paths, or protocol fields are available in the source data, these rules deliberately use vulnerability-class indicators (signal crashes, service aborts, unusual local IPC to the NeuroPilot context) rather than invented specifics. Rules should be tuned to the specific device telemetry available.

Sigma Rule

title: Potential Local Out-of-Bounds Write Against MediaTek NeuroPilot Service
id: 3f1c9b2e-7d4a-4c6e-9a11-8b5e2f0c6d21
status: experimental
description: Detects abnormal termination and crash patterns in NeuroPilot-related processes consistent with an out-of-bounds write (CWE-787) attempted against the MediaTek MT6881 NeuroPilot subsystem (CVE-2026-20523).
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-20523
author: valtersit.com
date: 2026/01/01
tags:
  - attack.privilege_escalation
  - attack.t1068
  - cve.2026-20523
logsource:
  category: process_creation
  product: linux
detection:
  selection_neuropilot:
    Image|contains:
      - 'neuropilot'
      - 'neuro_pilot'
      - 'npu'
  selection_crash_context:
    CommandLine|contains:
      - 'SIGSEGV'
      - 'SIGABRT'
      - 'SIGBUS'
  selection_crash_anomaly:
    EventType: 'coredump'
  condition: selection_neuropilot or (selection_crash_context and selection_crash_anomaly)
falsepositives:
  - Legitimate application crashes unrelated to exploitation
  - Firmware update or diagnostic tooling invoking NeuroPilot
level: medium

YARA Rule

rule CVE_2026_20523_MediaTek_NeuroPilot_OOB_Write_Indicators
{
    meta:
        author = "valtersit.com"
        description = "Heuristic indicator hunt for suspicious structures associated with the MediaTek NeuroPilot out-of-bounds write (CVE-2026-20523). Detects references to the affected subsystem and patch identifiers in binaries, firmware images, or forensic memory captures."
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-20523"
        reference_patch = "ALPS11249062"
        reference_issue = "MSV-9171"
        date = "2026-01-01"
        severity = "high"

    strings:
        $neuro1 = "neuropilot" ascii nocase wide
        $neuro2 = "NeuroPilot" ascii wide
        $patch = "ALPS11249062" ascii wide
        $issue = "MSV-9171" ascii wide
        $mt = "MT6881" ascii wide
        $bounds = "bounds check" ascii nocase wide

    condition:
        uint32be(0) == 0x7F454C46 or
        $patch or
        $issue or
        (2 of ($neuro*) and 1 of ($mt, $bounds))
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-20523 MediaTek NeuroPilot OOB Write - Oversized Payload to Local AI/NPU Service Channel"; flow:to_server,established; content:"neuropilot"; nocase; http_uri; pcre:"/(neuropilot|npu)[^\x0a]{0,64}(size|len|length|offset|count)=[0-9]{7,}/i"; threshold:type both, track by_src, count 5, seconds 60; reference:cve,2026-20523; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-20523; classtype:attempted-admin; sid:202620523; rev:1; metadata:created_at 2026_01_01, updated_at 2026_01_01, confidence Low, cve CVE-2026-20523;)

Elastic Detection

// Detects crash-driven exploitation attempts against MediaTek NeuroPilot (CVE-2026-20523).
// Tune process names to the actual NeuroPilot service binary observed on-device.
sequence by host.id, process.entity_id with maxspan=30s
  [ process where process.name : ("*neuropilot*", "*npu*", "*neuromodule*") and
      process.command_line != null ]
  [ process where event.type == "start" and process.name : ("tombstoned", "debuggerd", "crash_dump64", "crash_dump32", "systemd-coredump") and
      process.args : ("*neuropilot*", "*npu*") ]

Splunk SPL Query

index=android OR index=linux (source="*kern.log*" OR source="*syslog*" OR source="*logcat*")
(neuropilot OR neuro_pilot OR npu OR "MediaTek")
("SIGSEGV" OR "SIGABRT" OR "SIGBUS" OR "segfault" OR "out of bounds" OR "bounds" OR "AddressSanitizer" OR "buffer overflow" OR "tombstone")
| rex field=_raw "(?<crash_signal>SIG(SEGV|ABRT|BUS))"
| rex field=_raw "(?<fault_addr>fault addr [0-9a-fx]+)"
| stats count min(_time) as firstTime max(_time) as lastTime values(crash_signal) as signals values(fault_addr) as fault_addresses by host, source, process_name
| where count >= 3
| convert ctime(firstTime) ctime(lastTime)
| sort - count

Wazuh OSSEC Rule

<group name="cve_2026_20523,mediatak_neuropilot,">
  <rule id="2026523" level="10">
    <decoded_as>syslog</decoded_as>
    <match>neuropilot|neuro_pilot|npu</match>
    <match>SIGSEGV|SIGABRT|SIGBUS|segfault|out of bounds|buffer overflow|AddressSanitizer</match>
    <description>Possible local out-of-bounds write attempt against MediaTek NeuroPilot (CVE-2026-20523) - crash signature detected</description>
    <mitre>
      <id>T1068</id>
    </mitre>
    <group>privilege_escalation,cve_2026_20523,</group>
  </rule>

  <rule id="2026524" level="12">
    <if_sid>2026523</if_sid>
    <match>ALPS11249062|MSV-9171</match>
    <description>CVE-2026-20523 patch marker observed in NeuroPilot crash context - possible exploit targeting</description>
    <group>privilege_escalation,cve_2026_20523,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence is 0/4 — UNPATCHED. No patch evidence exists from any tracked source; the vendor fix field is N/A, no workarounds have been published, and no affected or fixed version range is available. The following guidance is therefore contingent and must be validated against a future vendor advisory.

1) Immediate mitigations (compensating controls, pending a patch):

• Restrict the ability to obtain arbitrary local code execution on MT6881 devices. Enforce strict application vetting and sideloading controls; the attack requires a local foothold (AV:L).
• Apply least-privilege and sandboxing policies so that untrusted applications cannot reach the NeuroPilot execution context. Where the platform supports per-process isolation of AI/NPU services, confirm it is enforced.
• Monitor for abnormal terminations and crash signatures in NeuroPilot-related processes; the detection content above is intended for this purpose.
• For high-assurance deployments, consider disabling or restricting access to the NeuroPilot/AI processing subsystem on devices where the functionality is not operationally required, until a patch is available.

2) Patch / upgrade steps (when available):

• Track MediaTek's advisory and the referenced patch identifier ALPS11249062 / issue MSV-9171. These identifiers are the authoritative pointers for the fix.
• Once the vendor publishes a fixed firmware build, validate the fixed version string against the affected MT6881 device population and stage updates through the device OEM's firmware update channel.
• Because no fixed version is currently mapped, do not assume that any given firmware build is patched on the basis of date alone. Confirm against vendor documentation.

3) Long-term hardening:

• Maintain an accurate inventory of MT6881-based devices to close the affected-version gap, since the vendor disclosed no version range.
• Require memory-safety hardening in firmware supply-chain requirements (bounds checking, ASan/MTE-style runtime checks where supported) for components processing externally influenced lengths and offsets.
• Integrate CVE-2026-20523 status checks into device patch-management baselines and re-evaluate EPSS/KEV status periodically in case exploit activity emerges.

Exploitation status. No exploitation in the wild is known. EPSS is 0.00133 (2.4th percentile). There is no CISA KEV listing, no public PoC, no Nuclei template, and no published exploit code. Residual risk is dominated by the unpatched state and the fact that exploitation requires only a local, unprivileged foothold with no user interaction.

References

1. NVD — CVE-2026-20523: https://nvd.nist.gov/vuln/detail/CVE-2026-20523
2. MITRE CWE-787 — Out-of-bounds Write: https://cwe.mitre.org/data/definitions/787.html
3. MITRE ATT&CK T1068 — Exploitation for Privilege Escalation: https://attack.mitre.org/techniques/T1068/
4. MediaTek Product Security / security advisory portal (consult for patch ID ALPS11249062 and issue MSV-9171): https://www.mediatek.com/security-and-compliance/product-security
5. CISA Known Exploited Vulnerabilities Catalog (verify current KEV status; CVE-2026-20523 was not listed at time of writing): https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Note on threat intelligence: at the time of writing, there is no reported threat actor campaign, no exploit-in-the-wild evidence, and no public proof-of-concept associated with CVE-2026-20523. The EPSS score (0.00133) and the absence of a CISA KEV entry indicate a low modeled near-term exploitation probability, which may change if the patch gaps identified above remain open and exploit tooling is published.