CVE-2025-56353 Denial of service in n/a
An attacker can cause denial of service in tinyMQTT by sending malformed UTF-8 topic filters that trigger unbounded memory allocation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-56353?
CVE-2025-56353 is a high-severity denial of service vulnerability in n/a, published on 20 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In tinyMQTT commit 6226ade15bd4f97be2d196352e64dd10937c1962 (2024-02-18), a memory leak occurs due to the broker's failure to validate or reject malformed UTF-8 strings in topic filters. An attacker can exploit this by sending repeated subscription requests with arbitrarily large or invalid filter payloads. Each request causes memory to be allocated for the malformed topic filter, but the broker does not free the associated memory, leading to unbounded heap growth and potential denial of service under sustained attack.
Weakness: CWE-401
Which versions are affected by CVE-2025-56353?
It affects 1 product.
Products include Justdoit0910 Tinymqtt.
How do I fix CVE-2025-56353?
No fix has been published for CVE-2025-56353 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-56353 being exploited?
There is no known exploitation of CVE-2025-56353 in the wild and no public exploit code.
Sources
Also known as GHSA-cqjp-pfhx-4jwv.