# CVE-2026-20403: Denial of service in MediaTek chipset

> A missing bounds check in MediaTek modem firmware allows remote attackers to cause a system crash via a rogue base station.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Feb 2026
- **Updated:** 30 Mar 2026
- **Also known as:** GHSA-2rrf-rvr2-f97v

## What is CVE-2026-20403?

CVE-2026-20403 is a medium-severity denial of service vulnerability in Mediatek Nr15, published on 2 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In Modem, there is a possible system crash due to a missing bounds check. This could lead to remote denial of service, 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: MOLY01689254 (Note: For N15 and NR16) / MOLY01689259 (Note: For NR17 and NR17R); Issue ID: MSV-4843.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-20403?

It affects 4 products.


Products: Mediatek Nr15, Mediatek Nr16, Mediatek Nr17, Mediatek Nr17r.

## How do I fix CVE-2026-20403?

Apply the vendor's patch.

## Is CVE-2026-20403 being exploited?

There is no known exploitation of CVE-2026-20403 in the wild and no public exploit code.

## Other vulnerabilities in Mediatek Nr15

- [CVE-2024-20082](https://insights.sbomify.com/CVE-2024-20082/): Memory corruption in MT2735, MT2737, MT6833, MT6835, MT6835T, MT6853, MT6855, MT6873, MT6875, MT6875T, MT6877, MT6879, MT6880, MT6883, MT6885, MT6886, MT6889, MT6890, MT6891, MT6893, MT6895, MT6895T, MT6896, MT6897, MT6980, MT6980D, MT6983, MT6985, MT6989, MT6990 (critical 9.8)
- [CVE-2025-20708](https://insights.sbomify.com/CVE-2025-20708/): Memory corruption in MT2735, MT2737, MT6813, MT6815, MT6833, MT6833P, MT6835, MT6835T, MT6853, MT6853T, MT6855, MT6855T, MT6873, MT6875, MT6875T, MT6877, MT6877T, MT6877TT, MT6878, MT6878M, MT6879, MT6880, MT6883, MT6885, MT6886, MT6889, MT6890, MT6891, MT6893, MT6895, MT6895TT, MT6896, MT6897, MT6899, MT6980, MT6980D, MT6983, MT6983T, MT6985, MT6985T, MT6989, MT6989T, MT6990, MT6991, MT8673, MT8675, MT8676, MT8678, MT8771, MT8791, MT8791T, MT8792, MT8795T, MT8797, MT8798, MT8863, MT8873, MT8883, MT8893 (high 8.8)
- [CVE-2024-20094](https://insights.sbomify.com/CVE-2024-20094/): Denial of service in MT2735, MT6833, MT6853, MT6855, MT6873, MT6875, MT6875T, MT6877, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8675, MT8771, MT8791, MT8791T, MT8797 (high 7.5)
- [CVE-2024-20003](https://insights.sbomify.com/CVE-2024-20003/): Denial of service in MT2735, MT6297, MT6833, MT6853, MT6855, MT6873, MT6875, MT6875T, MT6877, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8675, MT8791, MT8791T, MT8797 (high 7.5)
- [CVE-2024-20004](https://insights.sbomify.com/CVE-2024-20004/): Denial of service in MT2735, MT6297, MT6833, MT6853, MT6855, MT6873, MT6875, MT6875T, MT6877, MT6880, MT6883, MT6885, MT6889, MT6890, MT6891, MT6893, MT8675, MT8791, MT8791T, MT8797 (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20403 and fix it if it is affected.

What it is: CVE-2026-20403 is a medium-severity denial of service vulnerability in Mediatek Nr15, published on 2 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-20403 in the wild and no public exploit code.

Affected product: Mediatek Nr15. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-20403/ (Markdown: https://insights.sbomify.com/CVE-2026-20403/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20403
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20403
- OSV: https://osv.dev/vulnerability/CVE-2026-20403

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20403/
Summaries are generated and may contain mistakes; the official description above is the record.