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 all

Routine

MEDIUM 5.3WATCHLISTUPGRADE

CVE-2026-7423 is a medium-severity flaw (CVSS 5.3) affecting freertos-plus-tcp. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Adjacent network
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-191
Published	2026-04-29
Last modified	2026-10-26

Publisher (CNA): AMZN · Vendor: amazon

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-29 19:16 UTCPublished CVE record published
2026-10-26 20:10 UTCUpdated Record last modified

amazon freertos-plus-tcp UPGRADE

Affected: >= 4.0.0 and < 4.2.6 · >= 4.3.0 and < 4.4.1

Fixed in: 4.2.6, 4.4.1

Safe to downgrade to: a release before 4.0.0

1. Check installed version

apt-cache policy freertos-plus-tcp || rpm -q freertos-plus-tcp || freertos-plus-tcp --version

2. UPGRADE to 4.2.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade freertos-plus-tcp

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade freertos-plus-tcp

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 4.0.0 (Debian / Ubuntu)

apt-cache madison freertos-plus-tcp sudo apt install freertos-plus-tcp=<VERSION_BEFORE_4.0.0> sudo apt-mark hold freertos-plus-tcp

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list freertos-plus-tcp sudo dnf downgrade freertos-plus-tcp-<VERSION_BEFORE_4.0.0> sudo dnf versionlock add freertos-plus-tcp

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-7423?

freertos-plus-tcp: upgrade to 4.2.6, 4.4.1. Exact commands for each OS are on this page.

Is CVE-2026-7423 being exploited?

CVE-2026-7423 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-7423 affect?

CVE-2026-7423 affects freertos-plus-tcp. Severity is medium (CVSS 5.3). 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 siz

How urgent is CVE-2026-7423?

Priority 27/100. On your watchlist

Related CVEs

CVE-2026-7424 HIGH 8.1 UPGRADE Integer underflow in the DHCPv6 sub-option parser in FreeRTOS-Plus-TCP before V4.4.1 and V4.2.6 allows an adja
CVE-2026-7426 HIGH 8.1 UPGRADE Insufficient validation of the prefix length field in IPv6 Router Advertisement processing in FreeRTOS-Plus-TC
CVE-2026-7425 MEDIUM 6.5 UPGRADE Insufficient option length validation in the IPv6 Router Advertisement parser in FreeRTOS-Plus-TCP before V4.2
CVE-2026-7422 MEDIUM 6.5 UPGRADE Insufficient packet validation in FreeRTOS-Plus-TCP before V4.2.6 and V4.4.1 allows an adjacent network actor

References

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