VulnerabilityAnalyzed

CVE-2026-8686

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.

HIGH 8.7EPSS 0.39%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.39%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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 4.0: 8.7 HIGHCVSS:4.0/AV:N/AC:L/AT:N/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/M
EPSS: 0.39% probability · 32th percentile
CISA KEV: Not listed
Weakness: CWE-125
Affected: freertos/coremqtt
Source: ff89ba41-3aa1-4d27-914a-91399e9639e5

References

https://aws.amazon.com/security/security-bulletins/2026-032-aws/Vendor Advisory
https://github.com/FreeRTOS/coreMQTT/releases/tag/v5.0.1Release Notes
https://github.com/FreeRTOS/coreMQTT/security/advisories/GHSA-6qh9-r6jp-2wxcVendor Advisory

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.