# CVE-2026-102552: Amazon FreeRTOS-Plus-TCP DNS resolver source verification bypass

Source: https://junglewise.ai/threats/cve-2026-102552-improper-verification-of-the-source-of-a-communication-channel  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-16. Updated: 2026-10-16  
License: CC BY 4.0 with a link back

CVE-2026-102552 · Severity: medium · CVSS 5.9 · Published 2026-10-16

Amazon FreeRTOS-Plus-TCP is a network stack used in embedded and IoT devices to handle internet communications. An attacker on the network can forge DNS replies to redirect the device to malicious servers, potentially enabling data theft or interception of the device's connections by bypassing DNS security.

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-2026-102552 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-102552 being exploited in the wild.

**How severe is CVE-2026-102552?** Medium severity, with a CVSS score of 5.9, published 16 October 2026.

**Which products and versions are affected?** Amazon Freertos-Plus-Tcp before V4.4.2.

**Is there a fix for CVE-2026-102552?** Yes: fixed in V4.4.2. Until then: Upgrade to FreeRTOS-Plus-TCP V4.4.2 and enable ipconfigDNS_CHECK_REPLY_SOURCE_IP in FreeRTOSIPConfig.h. Alternatively, restrict the device to a trusted local resolver and protect the local network path to reduce exposure to off-path DNS reply forgery.</anigation>
<parameter name="timeline">[{"kind":"disclosed","at":"2026-10-16"}] Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-102552 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-102552?** Check whether you run Amazon Freertos-Plus-Tcp at an affected version. 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.

## How to fix

- Fixed in V4.4.2

Upgrade to FreeRTOS-Plus-TCP V4.4.2 and enable ipconfigDNS_CHECK_REPLY_SOURCE_IP in FreeRTOSIPConfig.h. Alternatively, restrict the device to a trusted local resolver and protect the local network path to reduce exposure to off-path DNS reply forgery.</anigation>
<parameter name="timeline">[{"kind":"disclosed","at":"2026-10-16"}]

## Technical details

The DNS resolver in FreeRTOS-Plus-TCP before V4.4.2 does not properly validate that DNS replies originate from the queried server, allowing an off-path attacker to inject forged DNS responses into the device's cache. The vulnerability requires network access and can be exploited without authentication. A fix exists in V4.4.2 with the mitigation requiring the ipconfigDNS_CHECK_REPLY_SOURCE_IP option to be explicitly enabled.

## Affected products

- Amazon FreeRTOS-Plus-TCP before V4.4.2

## References

- [https://aws.amazon.com/security/security-bulletins/2026-139-aws/](https://aws.amazon.com/security/security-bulletins/2026-139-aws/)
- [https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.4.2](https://github.com/FreeRTOS/FreeRTOS-Plus-TCP/releases/tag/V4.4.2)

## Related threats

- [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)
- [Integer underflow in the ICMP and ICMPv6 echo reply handlers in FreeRTOS-Plus-TCP before V4.4.1 and V4.2.6 allows an…](https://junglewise.ai/threats/cve-2026-7423-integer-underflow-in-the-icmp-and-icmpv6-echo-reply-handlers-in)