CVE Intelligence
High Memory corruption

CVE-2026-7426 — Out-of-Bounds Write via Unsanitized Prefix Length in Router Advertisement Processing in FreeRTOS-Plus-TCP

Insufficient validation of the prefix length field in IPv6 Router Advertisement processing in FreeRTOS-Plus-TCP before V4.2.6 and V4.4.1 allows an adjacent network actor to cause memory corruption by sending a crafted Router Advertisement with a prefix length value exceeding the maximum valid length, resulting in a heap buffer overflow. Users processing IPv4 RA only are not impacted. To mitigate this issue, users should upgrade to the fixed version when available.

Published Apr 29, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: AMZN

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.4% (30-day exploitation probability)+5
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.4%
ahead of 33% of scored CVEs · Oct 14, 2026
Affects
Amazon
Freertos-plus-tcp and 1 more
CVSS base
8.1
High · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Amazon Freertos-plus-tcp, AWS FreeRTOS-Plus-TCP).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Amazon Freertos-plus-tcp ≥ 4.0.0 and < 4.2.6≥ 4.3.0 and < 4.4.1 Vulnerable NIST National Vulnerability Database
AWS FreeRTOS-Plus-TCP ≥ 4.0.0 and < 4.2.6≥ 4.3.0 and < 4.4.1 Vulnerable CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

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

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.1 CVSS 4.0 Medium — — ff89ba41-3aa1-4d27-914a-91399e9639e5 via NIST National Vulnerability Database
6.1 CVSS 4.0 Medium — — AMZN via CVE Program (cve.org) e CISA ADP
8.1 CVSS 3.1 High 2.8 5.2 ff89ba41-3aa1-4d27-914a-91399e9639e5 via NIST National Vulnerability Database
8.1 CVSS 3.1 High — — AMZN via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H (score shown at the top: ff89ba41-3aa1-4d27-914a-91399e9639e5)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-787 · Out-of-bounds Write

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.40%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
endpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · aws/freertos-plus-tcp
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 8.1
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Apr 29, 2026 · AMZN

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

4 on the record

Elsewhere on this site

Amazon
every CVE for this vendor
Memory corruption
same class
CWE-787
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-7425 Out-of-Bounds Read in Router Advertisement Option Parser in FreeRTOS-Plus-TCP Apr 29, 2026
  • CVE-2026-7422 MAC Address Validation Bypass in FreeRTOS-Plus-TCP IPv4 and IPv6 Packet Processing Apr 29, 2026
  • CVE-2026-7423 Integer Underflow in ICMP Echo Reply Processing in FreeRTOS-Plus-TCP Apr 29, 2026
  • CVE-2026-7424 Integer Underflow in DHCPv6 Sub-Option Parser in FreeRTOS-Plus-TCP Apr 29, 2026
  • CVE-2025-11616 Buffer Over-read when receiving improperly sized ICMPv6 packets in FreeRTOS-Plus-TCP Oct 10, 2025
  • CVE-2025-11617 Buffer Over-read when receiving IPv6 packets with incorrect payload length in FreeRTOS-Plus-TCP Oct 10, 2025

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-7426 is "Out-of-Bounds Write via Unsanitized Prefix Length in Router Advertisement Processing in FreeRTOS-Plus-TCP", rated High. It affects Freertos-plus-tcp (Amazon); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 8.1 describes technical severity. EPSS 0.40% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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