CyberSecBulletin
CVE-2026-20521NVD status: Analyzed

MediaTek chipset: Stack-based Buffer Overflow

Published Updated By the CyberSecBulletin desk

CVE-2026-20521 is a high-severity stack-based buffer overflow vulnerability in MediaTek chipset from MediaTek, with a CVSS 3.1 base score of 8.4 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, without any action from a user. Affected MediaTek chipset versions: MT2718; MT6768; MT6769, and others listed below. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of MediaTek chipset you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on mediatek.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
MediaTekMediaTek chipsetMT2718; MT6768; MT6769; MT6781; MT6789; MT6833; MT6835; MT6853; and 32 more rangesNot stated
MediaTekMt8910 FirmwareNot specified in the recordNot stated
MediaTekMt2718 FirmwareNot specified in the recordNot stated
MediaTekMt6768 FirmwareNot specified in the recordNot stated
MediaTekMt6769 FirmwareNot specified in the recordNot stated
MediaTekMt6781 FirmwareNot specified in the recordNot stated
MediaTekMt6789 FirmwareNot specified in the recordNot stated
MediaTekMt6833 FirmwareNot specified in the recordNot stated
MediaTekMt6835 FirmwareNot specified in the recordNot stated
MediaTekMt6853 FirmwareNot specified in the recordNot stated
MediaTekMt6855 FirmwareNot specified in the recordNot stated
MediaTekMt6858 FirmwareNot specified in the recordNot stated
MediaTekMt6877 FirmwareNot specified in the recordNot stated
MediaTekMt6878 FirmwareNot specified in the recordNot stated
MediaTekMt6879 FirmwareNot specified in the recordNot stated
MediaTekMt6881 FirmwareNot specified in the recordNot stated
MediaTekMt6883 FirmwareNot specified in the recordNot stated
MediaTekMt6885 FirmwareNot specified in the recordNot stated
MediaTekMt6886 FirmwareNot specified in the recordNot stated
MediaTekMt6889 FirmwareNot specified in the recordNot stated
MediaTekMt6893 FirmwareNot specified in the recordNot stated
MediaTekMt6895 FirmwareNot specified in the recordNot stated
MediaTekMt6897 FirmwareNot specified in the recordNot stated
MediaTekMt6899 FirmwareNot specified in the recordNot stated
MediaTekMt6983 FirmwareNot specified in the recordNot stated

Version data comes from the organisation that assigned the CVE; 24 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CISA (ADP).

Official description

In Video HAL, there is a possible escalation of privilege due to a missing bounds check. This could lead to local escalation of privilege with no additional execution privileges needed. User interaction is not needed for exploitation. Patch ID: ALPS11375674; Issue ID: MSV-9571.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Stack-based Buffer Overflow

The product writes past the end of a buffer that was allocated on the stack.

How developers prevent this class of flaw

  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.
  • Use an abstraction library to abstract away risky APIs. Not a complete solution.
  • Implement and perform bounds checking on input.

More Stack-based Buffer Overflow vulnerabilities (CWE-121)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in MediaTek chipset

All MediaTek chipset vulnerabilities

Recent Stack-based Buffer Overflow vulnerabilities

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