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VulnerabilityPublished

CVE-2026-8686: FreeRTOS coreMQTT · Out-of-bounds Read

Affects FreeRTOS coreMQTTSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High · fixed in 5.0.1 : patch FreeRTOS coreMQTT soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 5.0.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 15 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
FreeRTOScoreMQTTAffected
  • =5.0.0
Fixed in–
GitHubfreertos/coreMQTTpkg:github/freertos/coreMQTTOther threatsAffected
  • =5.0.0
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should upgrade coreMQTT to version 5.0.1 or later to remediate this vulnerability. No other mitigations are specified. The vendor advisory confirms the availability of an official fix.

Description

CVE-2026-8686 is a high-severity vulnerability in FreeRTOS coreMQTT version 5.0.0. It involves a missing bounds validation in the MQTT v5.0 property parser, which allows an MQTT broker to cause a denial of service by sending a crafted packet. The issue is fixed in version 5.0.1.

References

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