CVE-2025-56352
TinyMQTT Broker Protocol Violation Leaving File Descriptors Open
Description
In tinyMQTT commit 6226ade15bd4f97be2d196352e64dd10937c1962 (2024-02-18), the broker mishandles protocol violations during CONNECT packet parsing. When receiving a CONNECT packet with a zero-length Client ID while CleanSession is set to 0, the broker correctly replies with a CONNACK return code 0x02 (Identifier Rejected) but fails to explicitly close the TCP connection. Since the surrounding connection teardown logic is not guaranteed to execute, each such invalid CONNECT attempt leaves the underlying socket open. Repeated attempts cause server-side resource exhaustion due to accumulating file descriptors and memory usage, potentially resulting in denial of service.
INFO
Published Date :
May 18, 2026, 4:16 p.m.
Last Modified :
May 18, 2026, 4:16 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2025-56352
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
Solution
- Ensure sockets close after rejecting invalid CONNECT packets.
- Implement robust connection teardown logic.
- Update the MQTT broker software.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-56352.
| URL | Resource |
|---|---|
| https://github.com/JustDoIt0910/tinyMQTT/issues/19 |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-56352 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-56352
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-56352 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-56352 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
May. 18, 2026
Action Type Old Value New Value Added Description In tinyMQTT commit 6226ade15bd4f97be2d196352e64dd10937c1962 (2024-02-18), the broker mishandles protocol violations during CONNECT packet parsing. When receiving a CONNECT packet with a zero-length Client ID while CleanSession is set to 0, the broker correctly replies with a CONNACK return code 0x02 (Identifier Rejected) but fails to explicitly close the TCP connection. Since the surrounding connection teardown logic is not guaranteed to execute, each such invalid CONNECT attempt leaves the underlying socket open. Repeated attempts cause server-side resource exhaustion due to accumulating file descriptors and memory usage, potentially resulting in denial of service. Added Reference https://github.com/JustDoIt0910/tinyMQTT/issues/19