CVE-2025-56353
CVE-2025-56353 is a high-severity vulnerability in Justdoit0910 Tinymqtt with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-401.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- EPSS exploit prediction: 0% (21st percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-3364
- Weakness: CWE-401
- Affected product: Justdoit0910 Tinymqtt
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2025-56353?
- 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.
- How severe is CVE-2025-56353?
- CVE-2025-56353 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
- Is CVE-2025-56353 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2025-56353?
- CVE-2025-56353 affects Justdoit0910 Tinymqtt. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2025-56353?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
- Does CVE-2025-56353 have an EU (EUVD) identifier?
- Yes. CVE-2025-56353 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-3364.
- When was CVE-2025-56353 published?
- CVE-2025-56353 was published on 2026-01-20 and last updated on 2026-06-17.
References
Affected products (1)
- cpe:2.3:a:justdoit0910:tinymqtt:2024-02-18:*:*:*:*:*:*:*
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