CVE-2026-20532

Executive Summary

CVE-2026-20532 is a double-free (CWE-415) vulnerability in the APU (AI Processing Unit) component of MediaTek MT6899 firmware. A local actor can trigger a memory corruption condition that crashes the APU subsystem, resulting in denial of service; no special execution privileges and no user interaction are required. Because exploitation is confined to the local attack surface (AV:L) and impacts availability only (A:H, C:N, I:N), the CVSS 3.1 base score is 6.2, and no public proof-of-concept, exploit code, or CISA KEV listing currently exists.

Technical Analysis

The vulnerability resides in the apu subsystem of the MediaTek MT6899 SoC firmware. Per the NVD description, the defect is a double free — memory that is released more than once — which is classified under CWE-415. In this class of flaw, a pointer to an allocated memory region is passed to a deallocation routine on two separate paths, so the second free operates on already-released memory. The allocator's internal metadata in that region can then be reused or reinterpreted, producing heap corruption that typically manifests as an immediate crash, or in more severe cases as controllable memory corruption.

The attack surface is the APU's local interfaces. The CVSS vector (AV:L/PR:N/UI:N) confirms the flaw is reachable from a local context without additional execution privileges and without any user interaction. The NVD text does not disclose the specific API, device node, driver entry point, or IPC message that reaches the vulnerable free path, so no function names, paths, or parameters can be stated with confidence. What is confirmed: the vulnerable code lives in the APU firmware/driver layer, the trigger is local, and the observable outcome stated by the vendor is an application crash leading to local denial of service.

The availability-only impact (A:H) means the primary demonstrated effect is loss of service continuity for the APU and any dependent workloads (on-device AI inference, camera/NPU pipelines), not confidentiality or integrity compromise. However, double-free bugs are notoriously exploitable for arbitrary write and privilege escalation when reliable heap shaping is achievable; the NVD assessment reflects what the vendor could demonstrate, not a hard ceiling on exploitability. The patch is identified by vendor Patch ID ALPS11249024, tracking issue MSV-9168, with no shipped version yet mapped by any tracked source (patch confidence 0/4).

Exploitation Scenarios

No public PoC exists; the chain below is described at the vulnerability-class level and drawn strictly from the NVD description.

1. Reconnaissance / target identification. The attacker must already have local execution on the device (e.g., a malicious app, a compromised process, or an ADB-reachable debug context). The target is any MediaTek MT6899 device running unpatched firmware that exposes the APU to local callers. Identification is via device fingerprinting — SoC model (MT6899 / Dimensity-class) and firmware build string.

2. Triggering the flaw. The attacker locates the local interface that drives APU allocation and teardown and issues requests that cause the same memory region to be freed twice. Because PR:N, no elevated permission is needed — a normal application-level local context suffices. The NVD description does not disclose the specific call sequence, message, or parameter that reaches the vulnerable free, so the exact trigger cannot be stated.

3. Execution method. This is a memory-corruption bug, not a code-injection or command-execution bug. The "payload" is the crafted request sequence itself. Unlike use-after-free exploitation, a double-free does not require a deliberate dangling pointer dereference; the corruption arises from the allocator's handling of the second release of the same chunk. With heap grooming (interleaving controlled allocations between the two frees), a determined attacker could in principle redirect allocator metadata — but no public technique for this specific APU path is documented.

4. Post-exploitation impact. As demonstrated by the vendor, the effect is a crash of the APU application/process — local denial of service. If the fault can be shaped reliably, the same primitive could support broader memory corruption; that escalation is theoretical here and unproven in public sources.

Impact Assessment

• Confidentiality (C:N) / Integrity (I:N): No stated impact. The demonstrated flaw does not read or modify protected data.
• Availability (A:H): High. Successful trigger crashes the APU service, causing local denial of service.
• Attack Vector (AV:L) / Privileges (PR:N) / User Interaction (UI:N): Local reachability with no privilege requirement and no user interaction — the bar to trigger is low once local execution is achieved.
• Base score: 6.2 (Medium).
• Blast radius: Devices shipping the MT6899 SoC with unpatched APU firmware. Impact is scoped to the device on which the local attacker already runs; there is no network amplification and no confirmed lateral movement.
• Business impact: For consumers, APU-dependent features (on-device AI, imaging) can be knocked offline. For enterprises, managed mobile fleets and embedded products using this SoC inherit the availability risk. Since there is no public exploit, PoC, or KEV status, near-term exploitation pressure is low (EPSS 0.00114, ~1.4th percentile).

Detection Guidance

Sigma Rule

title: Potential MediaTek APU Double-Free Crash / DoS (CVE-2026-20532)
id: 7c1e9b52-9f3a-4e21-b7d0-0a2c1f4e2053
status: experimental
description: Detects abnormal termination of MediaTek APU-related processes consistent with a double-free induced local denial of service.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-20532
author: valtersit.com
date: 2026/01/01
logsource:
  category: process_termination
  product: linux
detection:
  selection_proc:
    Image|endswith:
      - 'apu'
      - 'apu_daemon'
      - 'mtk_apu'
  selection_status:
    ExitCode:
      - 134
      - 139
      - 6
  condition: selection_proc and selection_status
falsepositives:
  - Legitimate APU process restarts during firmware updates
  - Debug builds with deliberately injected aborts
level: medium

YARA Rule

rule CVE_2026_20532_MediaTek_APU_DoubleFree
{
    meta:
        author = "valtersit.com"
        description = "Hunts MediaTek MT6899 APU firmware blobs referencing affected APU code; broad heuristic, refine before deployment"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-20532"
        cve = "CVE-2026-20532"
        date = "2026-01-01"
    strings:
        $apu1 = "apu" ascii wide nocase
        $mtk  = "MediaTek" ascii wide nocase
        $mtk2 = "MT6899" ascii wide
        $patch = "ALPS11249024" ascii wide
        $issue = "MSV-9168" ascii wide
    condition:
        (2 of ($apu1, $mtk, $mtk2)) and not ($patch or $issue)
}

Suricata IDS Rule

alert tcp any any -> any any (msg:"CVE-2026-20532 MediaTek APU Double-Free - local DoS indicator (correlated)"; flow:to_server; content:"|00|"; depth:1; classtype:attempted-dos; reference:cve,2026-20532; reference:url,nvd.nist.gov/vuln/detail/CVE-2026-20532; sid:202620532; rev:1; metadata:created_at 2026_01_01, affected_product MediaTek_MT6899;)

Elastic Detection

process where event.action in ("end", "terminated") and
  process.name : ("apu", "apu_daemon", "mtk_apu*") and
  process.exit_code in (6, 134, 139)

Splunk SPL Query

index=endpoint OR index=syslog ("apu" OR "mtk_apu" OR "apu_daemon")
| search (exit_code=134 OR exit_code=139 OR "double free" OR "SIGABRT")
| stats count min(_time) as first_seen max(_time) as last_seen
        by host, process_name, exit_code
| where count >= 1
| sort - last_seen

Wazuh OSSEC Rule

<group name="cve-2026-20532,mediatk,apu,">
  <rule id="2026205" level="7">
    <decoded_as>json</decoded_as>
    <field name="process.name">\.(apu|mtk_apu|apu_daemon)$</field>
    <field name="process.exit_code">^(134|139|6)$</field>
    <description>CVE-2026-20532: MediaTek APU process terminated abnormally (possible double-free induced DoS)</description>
    <options>no_full_log</options>
    <mitre>
      <id>T1203</id>
    </mitre>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 (UNPATCHED — no patch evidence from any tracked source).

1. Immediate mitigations.

   • Limit local attack surface: restrict sideloading and untrusted application installs, enforce strict app sandboxing, and disable ADB/debug interfaces on production MT6899 devices.
   • Where the APU/driver interface is separate, restrict access to it via SELinux policy or device policy so that only trusted system components can reach the vulnerable path.
   • Monitor for repeated abnormal terminations of APU-related processes as an indicator of a local DoS attempt.

2. Patch / upgrade steps.

   • Track MediaTek Patch ID ALPS11249024 and issue MSV-9168. Because no vendor advisory or shipped version reference is available in tracked sources, confirm patch availability directly with the OEM/SoC vendor.
   • Apply the OEM firmware update for MT6899 devices as soon as it integrates ALPS11249024; re-verify the firmware build string after update.

3. Long-term hardening.

   • Deploy memory-safety mitigations (e.g., hardened allocators, heap metadata protection) on the APU/driver layer where supported.
   • Integrate firmware SBOM tracking so MediaTek patch IDs flow into asset inventories and vulnerability scanners.
   • Extend mobile fleet management to detect and remediate SoC-level firmware vulnerabilities that classic OS patching misses.

References

• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20532
• CWE-415 Double Free: https://cwe.mitre.org/data/definitions/415.html
• MediaTek Product Security / Security Bulletin portal: https://www.mediatek.com/security
• MITRE ATT&CK T1203 Exploitation for Client Execution: https://attack.mitre.org/techniques/T1203/
• No CISA KEV entry, no public PoC, no exploit code, and no known threat actor campaign associated with this CVE as of this report.