Device crash via ICMP reply length underflow
Published Apr 29, 2026 · Updated Apr 29, 2026
Integer underflow in FreeRTOS-Plus-TCP 4.0.0 through 4.2.5 and 4.3.0 through 4.4.0 allows attackers to crash protected devices. The ICMP and ICMPv6 echo reply handlers subtract header sizes from an undersized packet length, wrapping it into a loop bound that reads beyond the network buffer. Exploitation requires adjacent-network access, outgoing ping support, and bypassed IP header validation; memory-protected devices crash without transmitting the out-of-bounds data.
Summary
What happened
Integer underflow in FreeRTOS-Plus-TCP 4.0.0 through 4.2.5 and 4.3.0 through 4.4.0 allows attackers to crash protected devices. The ICMP and ICMPv6 echo reply handlers subtract header sizes from an undersized packet length, wrapping it into a loop bound that reads beyond the network buffer. Exploitation requires adjacent-network access, outgoing ping support, and bypassed IP header validation; memory-protected devices crash without transmitting the out-of-bounds data.
The record
- CVE
- CVE-2026-7423
- Published
- Apr 29, 2026
- Updated
- Apr 29, 2026
- Vendor
- Amazon Web Services
- Product
- FreeRTOS-Plus-TCP
- Classifications
- CWE-191, T1499.004
- Attack vector
- adjacent
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 29, 2026CVE publishedPublication date reported by the CVE source.
- Apr 29, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=4.0.0 <4.2.6
- Affected versionversion=4.3.0 <4.4.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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