# CVE-2026-20540: MediaTek Modem out of bounds read vulnerability

Source: https://junglewise.ai/threats/cve-2026-20540-in-modem-there-is-a-possible-out-of-bounds-read-due-to-a-missing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-05. Updated: 2026-10-05  
License: CC BY 4.0 with a link back

CVE-2026-20540 · Severity: medium · CVSS 5.3 · Published 2026-10-05

A modem chipset used in smartphones and mobile devices contains a flaw that allows an attacker to read memory outside intended bounds. An attacker operating a rogue cellular base station could crash devices connected to it, causing denial of service without needing special privileges or user interaction.

Technologies: [MediaTek Dimensity 5G](https://junglewise.ai/threats/technologies/dimensity-5g), [MediaTek Helio 4G](https://junglewise.ai/threats/technologies/helio-4g). Vendors: [MediaTek](https://junglewise.ai/threats/vendors/mediatek).

## Quick answers

**Is CVE-2026-20540 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20540 being exploited in the wild.

**How severe is CVE-2026-20540?** Medium severity, with a CVSS score of 5.3, published 5 October 2026.

**Which products and versions are affected?** MediaTek Dimensity 5G; MediaTek Helio 4G; MediaTek 5G Modems.

**Is there a fix for CVE-2026-20540?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-20540 attacked?** It is attacked over the network, in device firmware.

**Am I affected by CVE-2026-20540?** Check whether you run MediaTek 5G Modems, MediaTek Dimensity 5G or MediaTek Helio 4G. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An out of bounds read vulnerability exists in the Modem subcomponent due to missing bounds checking. The vulnerability can be triggered remotely when a user equipment (UE) connects to an attacker-controlled rogue base station, requiring no additional privileges or user interaction for exploitation. This results in remote denial of service.

## Affected products

- MediaTek Dimensity 5G
- MediaTek Helio 4G
- MediaTek 5G Modems

## Timeline

- 2026-10-05: disclosed

## References

- [https://www.mediatek.com/product-security-bulletin/October-2026](https://www.mediatek.com/product-security-bulletin/October-2026)

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- [MediaTek display system crash due to logic error](https://junglewise.ai/threats/cve-2026-20590-in-display-there-is-a-possible-system-crash-due-to-a-logic-error)
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