CVE-2020-36406Network attack vector

Memory corruption via triggered-topic array overflow

Published Jul 1, 2021 · Updated Aug 4, 2024

Stack-based buffer overflow in uWebSockets 18.11.0 and 18.12.0 allows remote attackers to corrupt memory via MQTT wildcard use. TopicTree queues triggered-topic pointers in a fixed 64-entry array but checks its limit only at function entry, so one publish matching too many wildcards writes past the array. Reachability requires exposed pub/sub behavior and more than 64 triggered wildcard topics; the vendor disputes the issue's security significance.

CVSS severity8.8
High
EPSS probability1.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stack-based buffer overflow in uWebSockets 18.11.0 and 18.12.0 allows remote attackers to corrupt memory via MQTT wildcard use. TopicTree queues triggered-topic pointers in a fixed 64-entry array but checks its limit only at function entry, so one publish matching too many wildcards writes past the array. Reachability requires exposed pub/sub behavior and more than 64 triggered wildcard topics; the vendor disputes the issue's security significance.

The record

CVE
CVE-2020-36406
Published
Jul 1, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 1, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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