Integer Underflow in FreeRTOS-Plus-TCP ICMP Handlers V4.4.1/V4.2.6
CVE-2026-7423 Published on April 29, 2026
Integer Underflow in ICMP Echo Reply Processing in FreeRTOS-Plus-TCP
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.
Vulnerability Analysis
Weakness Type
What is an Integer underflow Vulnerability?
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This can happen in signed and unsigned cases.
CVE-2026-7423 has been classified to as an Integer underflow vulnerability or weakness.
Products Associated with CVE-2026-7423
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Affected Versions
AWS FreeRTOS-Plus-TCP:- Version 4.0.0 and below 4.2.6 is affected.
- Version 4.3.0 and below 4.4.1 is affected.
- Version 4.2.6 is unaffected.
- Version 4.4.1 is unaffected.