# CVE-2026-20539: MediaTek Modem out of bounds read due to missing bounds check

Source: https://junglewise.ai/threats/cve-2026-20539-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-2026-20539 · Severity: medium · CVSS 5.3 · Published 2026-10-05

MediaTek modems used in smartphones and other devices contain an out of bounds read vulnerability due to insufficient input validation. An attacker operating a rogue cellular base station can trigger a denial of service condition by sending specially crafted network packets, crashing the modem without requiring the user to take any action or have special privileges.

Technologies: [MediaTek MT2716 Modem](https://junglewise.ai/threats/technologies/mt2716-modem), [MediaTek MT2735 Modem](https://junglewise.ai/threats/technologies/mt2735-modem), [MediaTek MT2737 Modem](https://junglewise.ai/threats/technologies/mt2737-modem), [MediaTek MT6813 Modem](https://junglewise.ai/threats/technologies/mt6813-modem), [MediaTek MT6815 Modem](https://junglewise.ai/threats/technologies/mt6815-modem), [MediaTek MT6833 Modem](https://junglewise.ai/threats/technologies/mt6833-modem), [MediaTek MT6835 Modem](https://junglewise.ai/threats/technologies/mt6835-modem), [MediaTek MT6853 Modem](https://junglewise.ai/threats/technologies/mt6853-modem), [MediaTek MT6855 Modem](https://junglewise.ai/threats/technologies/mt6855-modem), [MediaTek MT6858 Modem](https://junglewise.ai/threats/technologies/mt6858-modem), [MediaTek MT6873 Modem](https://junglewise.ai/threats/technologies/mt6873-modem), [MediaTek MT6875 Modem](https://junglewise.ai/threats/technologies/mt6875-modem), [MediaTek MT6877 Modem](https://junglewise.ai/threats/technologies/mt6877-modem), [MediaTek MT6878 Modem](https://junglewise.ai/threats/technologies/mt6878-modem), [MediaTek MT6879 Modem](https://junglewise.ai/threats/technologies/mt6879-modem), [MediaTek MT6880 Modem](https://junglewise.ai/threats/technologies/mt6880-modem), [MediaTek MT6881 Modem](https://junglewise.ai/threats/technologies/mt6881-modem), [MediaTek MT6883 Modem](https://junglewise.ai/threats/technologies/mt6883-modem), [MediaTek MT6885 Modem](https://junglewise.ai/threats/technologies/mt6885-modem), [MediaTek MT6886 Modem](https://junglewise.ai/threats/technologies/mt6886-modem), [MediaTek MT6889 Modem](https://junglewise.ai/threats/technologies/mt6889-modem), [MediaTek MT6890 Modem](https://junglewise.ai/threats/technologies/mt6890-modem), [MediaTek MT6891 Modem](https://junglewise.ai/threats/technologies/mt6891-modem), [MediaTek MT6893 Modem](https://junglewise.ai/threats/technologies/mt6893-modem), [MediaTek MT6895 Modem](https://junglewise.ai/threats/technologies/mt6895-modem), [MediaTek MT6896 Modem](https://junglewise.ai/threats/technologies/mt6896-modem). Vendors: [MediaTek](https://junglewise.ai/threats/vendors/mediatek).

## Quick answers

**Is CVE-2026-20539 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-20539 being exploited in the wild.

**How severe is CVE-2026-20539?** Medium severity, with a CVSS score of 5.3, published 5 October 2026.

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

**Is there a fix for CVE-2026-20539?** 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-2026-20539 attacked?** It is attacked over the network, in device firmware.

**Am I affected by CVE-2026-20539?** Check whether you run MediaTek MT2716 Modem, MediaTek MT2735 Modem, MediaTek MT2737 Modem 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 subcomponent allows an out of bounds read when processing base station communications. The vulnerability is remotely exploitable by an attacker controlling a rogue base station and does not require user interaction or device-level privileges. Successful exploitation causes denial of service through modem crash.

## Affected products

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

## 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 Modem out-of-bounds write](https://junglewise.ai/threats/cve-2026-20526-in-modem-there-is-a-possible-out-of-bounds-write-due-to-a-missing)
- [MediaTek Modem out-of-bounds write](https://junglewise.ai/threats/cve-2026-20519-in-modem-there-is-a-possible-out-of-bounds-write-due-to-a-missing)
- [MediaTek Modem system crash due to improper input validation](https://junglewise.ai/threats/cve-2026-20500-mediatek-modem-system-crash-due-to-improper-input-validation)