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CVE-2026-7423· NVD / CVE Program· CNA AMZN

Integer Underflow in ICMP Echo Reply Processing in FreeRTOS-Plus-TCP

Noroxi assessment

Priority: Monitor (action score 24/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.35% (FIRST EPSS).
  • Someone on the same network segment can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: AWS FreeRTOS-Plus-TCP 4.2.6, 4.4.1.

Low priority for now. Upgrade to AWS FreeRTOS-Plus-TCP 4.2.6, 4.4.1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 6.0 · v4.0—No exploit Fix available
Published
Apr 29, 2026
Updated
Jun 17, 2026
EPSS
0.3% · 28th percentile

Report tools

JSON

Action score

24

Monitor

Low priority for now.

CVSS
24 / 40 · 6.0 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · AMZN
5.3
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:3.1/AV:A/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-7423

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
amazonfreertos-plus-tcp

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • amazon freertos-plus-tcp4.0.0 and later · before 4.2.6
  • amazon freertos-plus-tcp4.3.0 and later · before 4.4.1

Versions reported by the vendor

Affected version ranges reported by the assigning authority (AMZN). Independent of NVD's CPE analysis and usually ahead of it.

  • AWS FreeRTOS-Plus-TCP

    • 4.2.6, 4.4.1not affected
    • 4.0.0 and later · before 4.2.6affected · semver
    • 4.3.0 and later · before 4.4.1affected · semver

Same product

amazon: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-38373FreeRTOS-Plus-TCP Buffer Over-Read in DNS Response Parser
    32Monitor
  • CVE-2026-7424Integer Underflow in DHCPv6 Sub-Option Parser in FreeRTOS-Plus-TCP
    28Monitor
  • CVE-2026-7422MAC Address Validation Bypass in FreeRTOS-Plus-TCP IPv4 and IPv6 Packet Processing
    28Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2025-11617Oct 10, 2025 · Buffer Over-read when receiving IPv6 packets with incorrect payload length in FreeRTOS-Plus-TCP
    21Monitor
  • ← EarlierCVE-2025-11618Oct 10, 2025 · Invalid Pointer Dereference when receiving UDP/IPv6 packets in FreeRTOS-Plus-TCP
    21Monitor
  • Later →CVE-2026-7425Apr 29, 2026 · Out-of-Bounds Read in Router Advertisement Option Parser in FreeRTOS-Plus-TCP
    24Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
AWS FreeRTOS-Plus-TCP4.2.6Vendor (CNA)
AWS FreeRTOS-Plus-TCP4.4.1Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-74240 days apartInteger Underflow in DHCPv6 Sub-Option Parser in FreeRTOS-Plus-TCP
    28Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Someone on the same network segment can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Adjacent
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-191 · Integer Underflow (Wrap or Wraparound)

CVSS vector

CVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records