# CVE-2026-7423: Integer underflow in the ICMP and ICMPv6 echo reply handlers in FreeRTOS-Plus-TCP before V4.4.1 and V4.2.6 allows an…

Source: https://junglewise.ai/threats/cve-2026-7423-integer-underflow-in-the-icmp-and-icmpv6-echo-reply-handlers-in  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-29  
License: CC BY 4.0 with a link back

CVE-2026-7423 · Severity: medium · CVSS 5.3 · Published 2026-04-29

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.

Technologies: [Amazon Freertos-Plus-Tcp](https://junglewise.ai/threats/technologies/amazon-freertos-plus-tcp). Vendors: [Amazon](https://junglewise.ai/threats/vendors/amazon).

## Quick answers

**Is CVE-2026-7423 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-7423 being exploited in the wild.

**How severe is CVE-2026-7423?** Medium severity, with a CVSS score of 5.3, published 29 April 2026.

**Which products and versions are affected?** Amazon Freertos-Plus-Tcp. The advisory does not name versions.

**Is there a fix for CVE-2026-7423?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**Am I affected by CVE-2026-7423?** Check whether you run Amazon Freertos-Plus-Tcp. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Amazon Freertos-Plus-Tcp

## Related threats

- [Amazon FreeRTOS-Plus-TCP DNS resolver source verification bypass](https://junglewise.ai/threats/cve-2026-102552-improper-verification-of-the-source-of-a-communication-channel)
- [FreeRTOS-Plus-TCP improper source verification in IPv6 Router Advertisement and DNS resolver](https://junglewise.ai/threats/cve-2026-102551-amp-issue-with-freertos-plus-tcp)
- [Insufficient validation of the prefix length field in IPv6 Router Advertisement processing in FreeRTOS-Plus-TCP before…](https://junglewise.ai/threats/cve-2026-7426-insufficient-validation-of-the-prefix-length-field-in-ipv6-router)
- [Amazon FreeRTOS-Plus-TCP memory safety issues in IPv6 Router Advertisement](https://junglewise.ai/threats/cve-2026-7425-amazon-freertos-plus-tcp-memory-safety-issues-in-ipv6-router)
- [Amazon FreeRTOS-Plus-TCP integer underflow in DHCPv6 parser](https://junglewise.ai/threats/cve-2026-7424-amazon-freertos-plus-tcp-integer-underflow-in-dhcpv6-parser)