CVE-2025-56353
Justdoit0910 Tinymqtt 2024-02-18
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2025-56353 is a high-severity Missing Release of Memory after Effective Lifetime (CWE-401) vulnerability in Justdoit0910 Tinymqtt. Its CVSS base score is 7.5 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Endpoint Denial of Service (T1499); ranked at the 21th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-56353 is a memory leak vulnerability in the tinyMQTT broker at commit 6226ade15bd4f97be2d196352e64dd10937c1962, dated 2024-02-18. The issue stems from the broker's failure to validate or reject malformed UTF-8 strings in topic filters, resulting in memory allocation for each malformed filter without subsequent deallocation. This affects the heap, as classified under CWE-401 (Memory Leak), with a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
A remote, unauthenticated attacker can exploit this vulnerability over the network with low complexity and no user interaction required. By sending repeated MQTT subscription requests containing arbitrarily large or invalid topic filter payloads, the attacker triggers ongoing memory allocation for each request. The broker does not free this memory, causing unbounded heap growth and eventual denial of service through resource exhaustion under sustained attack.
Mitigation details and further discussion are available in the GitHub issue at https://github.com/JustDoIt0910/tinyMQTT/issues/19. The vulnerability was published on 2026-01-20.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-3364
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (static analysis, fuzzing, or runtime leak detection) directly finds missing deallocation.
Requiring documented development standards and tools can mandate memory-management disciplines that avoid leaks at introduction.
Engineering principles applied during development can require explicit resource-release patterns that stop memory leaks from being coded.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly enforce proper memory allocation/deallocation via coding standards, reviews, and tooling.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development can detect unreleased memory, providing partial coverage of the weakness.
Secure development life cycle mandates memory-management practices that reduce missing-release defects.
Application security requirements can specify explicit memory-release rules, partially mitigating the weakness.
Secure system architecture and engineering principles include resource-management guidelines that address memory leaks.
Secure coding standards directly require proper allocation/deallocation, covering most of this weakness.
Capacity management may detect memory exhaustion symptoms but does not prevent the coding flaw.