Cyber Resilience

CVE-2026-20521

Memory Safety in Mediatek Mt8910 Firmware

Memory Safety
Published
05 October 2026
Modified
08 October 2026
Patch / advisory
View advisory
CVSS Score v3.1 8.4
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.0013 3th percentile
Risk Priority 59 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-20521 is a high-severity Stack-based Buffer Overflow (CWE-121) vulnerability in Mediatek Mt8910 Firmware. Its CVSS base score is 8.4 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked at the 3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

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;…

more

Issue ID: MSV-9571.

CWE(s)
CWE-121

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-20501Same product: Mediatek Mt2718
CVE-2026-20502Same product: Mediatek Mt2718
CVE-2025-20794Same product: Mediatek Mt6833
CVE-2026-20586Same product: Mediatek Mt2718
CVE-2026-20449Same product: Mediatek Mt6768
CVE-2026-20451Same product: Mediatek Mt2718
CVE-2026-20453Same product: Mediatek Mt6768
CVE-2026-20455Same product: Mediatek Mt6768
CVE-2026-20519Same product: Mediatek Mt6833
CVE-2026-20520Same product: Mediatek Mt6833

Affected Assets

mediatek
mt8910 firmware
all versions
mediatek
mt2718 firmware
all versions
mediatek
mt6768 firmware
all versions
mediatek
mt6769 firmware
all versions
mediatek
mt6781 firmware
all versions
mediatek
mt6789 firmware
all versions
mediatek
mt6833 firmware
all versions
mediatek
mt6835 firmware
all versions
mediatek
mt6853 firmware
all versions
mediatek
mt6855 firmware
all versions
+38 more product configuration(s) — see NVD for full list

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 2 hardening rules · 2 OS baselines
Validate
Prove the fix (OWASP ASVS)

—

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation partial match

Developer testing and analysis can discover stack-buffer overflows before deployment.

SA-8 Security and Privacy Engineering Principles partial match

Secure-engineering principles include bounds-checked coding and safe buffer handling that avoid introducing the flaw.

SI-10 Information Input Validation partial match

Input validation directly stops untrusted data from exceeding stack buffer bounds.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

ID.RA-01 partial match
blocks

Vulnerability scanning can discover stack buffer overflows but does not prevent their introduction.

PR.PS-02 partial match
blocks

Patching eliminates known instances of the weakness after discovery.

PR.PS-06 partial match
blocks

Secure-development practices directly prevent introduction of stack buffer overflows.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.5.14 Information transfer partial match
removes
A.5.15 Access control partial match
removes
A.5.16 Identity management partial match
removes
A.5.17 Authentication information partial match
removes
A.5.18 Access rights partial match
removes
A.8.10 Information deletion partial match
removes

Hardening callouts derived

Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).

Oracle Linux 8 (1 rule)
  • V-248594 OL 8 must implement address space layout randomization (ASLR) to protect its memory from unauthorized code execution. blocks CWE-121
Oracle Linux 9 (1 rule)
  • V-271452 OL 9 must use a Linux Security Module configured to enforce limits on system services. blocks CWE-121

References