9.1

CVE-2026-8686: freertos coremqtt Out-of-bounds Read

CVSS: 9.1v3.1CriticalAnalyzed
Published 15-05-2026Last modified 15-05-2026
Open JSON

Vulnerability summary

CVE-2026-8686 is a critical (CVSS 9.1) Out-of-bounds Read vulnerability in freertos coremqtt. EPSS estimates a 0.68% chance of exploitation in the next 30 days, higher than 51.6% of scored vulnerabilities.

Overall risk
70/100
0100
High · default modelHow is this calculated?
CVSS score
9.1/10
010
Critical · v3.1 (NVD)
EPSS score
0.68%
0%100%
Low · +0.29 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Timeline

  1. 15-05-2026
    PublishedVulnerability first disclosed.
  2. 15-05-2026
    Last modifiedVulnerability information updated.

Description

Missing bounds validation in the MQTT v5.0 property parser in coreMQTT before 5.0.1 allows an MQTT broker to cause a denial of service by sending a crafted packet. To remediate this issue, users should upgrade to v5.0.1.

CVSS metrics

4 scores · 2 sources · 2 versions

EPSS trend

Probability

0.68%

Chance of exploitation in the next 30 days

Percentile

52%

Versus all other CVEs

30-day change

+0.29 pp

From 0.39% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.68%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Freertos1 product

1 vendor · 1 product

References

3 links