TI-2026-83698 Aliases CVE-2026-20557 GHSA-f3f6-67rr-rmf6

Out-of-bounds write in MediaTek modem allows privilege escalation

LOW 34CWE-787Published 2026-11-02 · Updated 2026-11-04

Key facts

Attack vector: Adjacent network
Privileges required: None
User interaction: None
Attack complexity: High
Impact type: Code execution
Confidentiality · integrity · availability: High · High · High
Fix status: No fix listed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-787 and the CVSS impact.

Summary

CVE-2026-20557 (GHSA-f3f6-67rr-rmf6) is an out-of-bounds write (CWE-787) in the modem of MediaTek chipsets, caused by a missing bounds check. If a UE has connected to a rogue base station controlled by an attacker, the flaw can lead to remote escalation of privilege, with no additional execution privileges and no user interaction. CVSS 3.1 scores it 7.5 (HIGH) with the vector CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. The affected chipsets include MT2716, MT6813, MT6815, MT6835, MT6858 and other models, and no fix is listed.

Written with Claude Haiku 5.5 from the sources below · 2026-11-03

Description from the CNA

In Modem, there is a possible out of bounds write due to a missing bounds check. This could lead to remote escalation of privilege, if a UE has connected to a rogue base station controlled by the attacker, with no additional execution privileges needed. User interaction is not needed for exploitation. Patch ID: MOLY01877236; Issue ID: MSV-9804.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00232 14th percentileScored 2026-11-07

Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
MediaTek	MediaTek chipset	MT2716; MT6813; MT6815; MT6835; MT6858; MT6878; MT6881; MT6897; MT6899; MT6982; MT6986; MT6988; MT6991; MT6993; MT8668; MT8676; MT8678; MT8755; MT8775; MT8792; MT8793; MT8863; MT8873; MT8875; MT8883	—	No fix listed	CNA

MediaTek chipset VendorMediaTek Affected MT2716; MT6813; MT6815; MT6835; MT6858; MT6878; MT6881; MT6897; MT6899; MT6982; MT6986; MT6988; MT6991; MT6993; MT8668; MT8676; MT8678; MT8755; MT8775; MT8792; MT8793; MT8863; MT8873; MT8875; MT8883 Fixed in — No fix listed CNA

Remediation

Written with Claude Haiku 5.5 from the sources below · 2026-11-03

Timeline

2026-11-02 Threatist record created from CVE-2026-20557
2026-11-02 Alias added: GHSA-f3f6-67rr-rmf6
2026-11-02 CVSS score added · CISA ADP
2026-11-02 CISA SSVC decision points changed
2026-11-03 CISA SSVC decision points changed
2026-11-03 CISA SSVC decision points changed
2026-11-04 CISA SSVC decision points changed

References

Other 1

https://www.mediatek.com/product-security-bulletin/November-2026

TI-2020-00067 Out-of-bounds write in Android KEVCVSS 3.1HIGH 7.8
TI-2024-13053 Improper input validation in MediaTek MT6890, MT7915, MT7916, MT7981, MT7986 CVSS 3.1CRITICAL 9.8
TI-2025-14725 Integer overflow in MediaTek MT6781, MT6789, MT6835, MT6855, MT6878, MT6879, MT6886… CVSS 3.1MEDIUM 6.5
TI-2024-13114 Memory corruption in MediaTek MT2735, MT2737, MT6833, MT6835, MT6835T, MT6853, MT6855… CVSS 3.1CRITICAL 9.8
TI-2022-14283 Command injection in MediaTek EN7528, EN7580 CVSS 3.1CRITICAL 9.8
TI-2021-11684 Command injection in MediaTek EN7528, EN7580 CVSS 3.1CRITICAL 9.8

See all 1133 →

Sources

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