Vulnerability · Published Apr 29, 2026 · Assigned by AMZN

CVE-2026-7423Integer Underflow in ICMP Echo Reply Processing in FreeRTOS-Plus-TCP

Medium 5.3

In plain English

A medium-severity security flaw in FreeRTOS-Plus-TCP from AWS. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 13% of all known vulnerabilities).

Severity (CVSS 3.1)5.3Medium

Exploit odds (30 days)0.2%top 87.2% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Integer underflow in the ICMP and ICMPv6 echo reply handlers in FreeRTOS-Plus-TCP before V4.4.1 and V4.2.6 allows an adjacent network user to cause a denial of service (device crash) when outgoing ping support is enabled, because header sizes are subtracted from a packet length field without validating the field is large enough, resulting in a heap out-of-bounds read of up to approximately 65KB. To mitigate this issue, users should upgrade to the fixed version when available.

Affected products (as reported)

Vendor	Product	Versions
AWS	FreeRTOS-Plus-TCP	4.0.0 – before 4.2.64.3.0 – before 4.4.1

Weakness: CWE-191 · Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

References

https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.4.1 patch
https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.2.6 patch
https://aws.amazon.com/security/security-bulletins/2026-021-aws/ vendor-advisory
https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/security/advisories/GHSA-7r59-2pgv-9v2r third-party-advisory