# CVE-2026-20520: MediaTek Modem out of bounds write in Modem

Source: https://junglewise.ai/threats/cve-2026-20520-in-modem-there-is-a-possible-out-of-bounds-write-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-2026-20520 · Severity: high · CVSS 7.5 · Published 2026-10-05

MediaTek modems used in smartphones and wireless devices contain an out-of-bounds write vulnerability that lacks proper input validation. An attacker controlling a rogue cellular base station can trigger this flaw to gain full device privileges without any user interaction or authentication. This could allow complete device compromise and data exfiltration.

Technologies: [MediaTek Mt2716](https://junglewise.ai/threats/technologies/mt2716), [MediaTek MT2735](https://junglewise.ai/threats/technologies/mt2735), [MediaTek MT2737](https://junglewise.ai/threats/technologies/mt2737), [MediaTek MT6813](https://junglewise.ai/threats/technologies/mt6813), [MediaTek Mt6815](https://junglewise.ai/threats/technologies/mt6815), [MediaTek MT6833](https://junglewise.ai/threats/technologies/mt6833), [MediaTek Mt6835](https://junglewise.ai/threats/technologies/mt6835), [MediaTek Mt6853](https://junglewise.ai/threats/technologies/mt6853), [MediaTek Mt6855](https://junglewise.ai/threats/technologies/mt6855), [MediaTek MT6858](https://junglewise.ai/threats/technologies/mt6858), [MediaTek MT6873](https://junglewise.ai/threats/technologies/mt6873), [MediaTek Mt6875](https://junglewise.ai/threats/technologies/mt6875), [MediaTek Mt6877](https://junglewise.ai/threats/technologies/mt6877), [MediaTek Mt6878](https://junglewise.ai/threats/technologies/mt6878), [MediaTek Mt6879](https://junglewise.ai/threats/technologies/mt6879), [MediaTek Mt6880](https://junglewise.ai/threats/technologies/mt6880), [MediaTek Mt6881](https://junglewise.ai/threats/technologies/mt6881), [MediaTek Mt6883](https://junglewise.ai/threats/technologies/mt6883), [MediaTek Mt6885](https://junglewise.ai/threats/technologies/mt6885), [MediaTek Mt6886](https://junglewise.ai/threats/technologies/mt6886), [MediaTek Mt6889](https://junglewise.ai/threats/technologies/mt6889), [MediaTek Mt6890](https://junglewise.ai/threats/technologies/mt6890), [MediaTek MT6891](https://junglewise.ai/threats/technologies/mt6891), [MediaTek Mt6893](https://junglewise.ai/threats/technologies/mt6893), [MediaTek Mt6895](https://junglewise.ai/threats/technologies/mt6895), [MediaTek MT6896](https://junglewise.ai/threats/technologies/mt6896). Vendors: [MediaTek](https://junglewise.ai/threats/vendors/mediatek).

## Quick answers

**Is CVE-2026-20520 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20520 being exploited in the wild.

**How severe is CVE-2026-20520?** High severity, with a CVSS score of 7.5, published 5 October 2026.

**Which products and versions are affected?** MediaTek MT2716; MediaTek MT2735; MediaTek MT2737; MediaTek MT6813; and 22 more.

**Is there a fix for CVE-2026-20520?** 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-2026-20520 attacked?** It is attacked over the network, in device firmware.

**Am I affected by CVE-2026-20520?** Check whether you run MediaTek Mt2716, MediaTek MT2735, MediaTek MT2737 or one of the others listed. 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

A missing bounds check in the modem component allows an out-of-bounds write (CWE-787) when processing certain cellular protocol messages. An attacker can exploit this via a malicious base station a device connects to, without needing to bypass any authentication or user interaction. Successful exploitation grants remote privilege escalation on the affected device.

## Affected products

- MediaTek MT2716
- MediaTek MT2735
- MediaTek MT2737
- MediaTek MT6813
- MediaTek MT6815
- MediaTek MT6833
- MediaTek MT6835
- MediaTek MT6853
- MediaTek MT6855
- MediaTek MT6858
- MediaTek MT6873
- MediaTek MT6875
- MediaTek MT6877
- MediaTek MT6878
- MediaTek MT6879
- MediaTek MT6880
- MediaTek MT6881
- MediaTek MT6883
- MediaTek MT6885
- MediaTek MT6886
- MediaTek MT6889
- MediaTek MT6890
- MediaTek MT6891
- MediaTek MT6893
- MediaTek MT6895
- MediaTek MT6896

## Timeline

- 2026-10-05: disclosed

## References

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

## Related threats

- [MediaTek ccci out of bounds write](https://junglewise.ai/threats/cve-2026-20552-in-ccci-there-is-a-possible-out-of-bounds-write-due-to-a-missing)
- [MediaTek vdec out-of-bounds write in type confusion](https://junglewise.ai/threats/cve-2026-20579-in-vdec-there-is-a-possible-out-of-bounds-write-due-to-type)
- [MediaTek out of bounds write in modem](https://junglewise.ai/threats/cve-2026-20544-in-meta-there-is-a-possible-out-of-bounds-write-due-to-a-missing)
- [MediaTek Modem information disclosure due to logic error](https://junglewise.ai/threats/cve-2026-20543-in-modem-there-is-a-possible-information-disclosure-due-to-a)
- [MediaTek Modem out-of-bounds read due to missing permission check](https://junglewise.ai/threats/cve-2026-20538-in-modem-there-is-a-possible-out-of-bounds-read-due-to-a-missing)