CVE-2025-6498 is a memory leak vulnerability identified in version 5.8.0 of tidy-html5, an open-source HTML parser and pretty printer maintained by HTACG. The flaw exists in the function defaultAlloc within the source file src/alloc.c. The vulnerability arises from improper memory management during allocation, leading to a memory leak when the function is manipulated. This leak can cause the affected application to consume increasing amounts of memory over time, potentially degrading system performance or causing denial of service due to resource exhaustion. The attack vector is local, meaning an attacker must have local access to the host to exploit the vulnerability. No user interaction or authentication beyond local privileges is required. The CVSS 4.0 base score is 4.8, reflecting a medium severity level, with the vector indicating low attack complexity, low privileges required, no user interaction, and limited impact on confidentiality, integrity, and availability. Although the exploit has been publicly disclosed, there are no known exploits in the wild at this time. The vulnerability does not affect confidentiality or integrity directly but impacts availability through resource leakage. The scope is limited to systems running the specific vulnerable version of tidy-html5, which is commonly used in software development, web content processing, and automated HTML cleanup tasks. No patches or fixes have been linked yet, so mitigation relies on workarounds or upgrading when a fix is released.

For European organizations, the impact of CVE-2025-6498 is primarily related to system stability and availability. Organizations that integrate tidy-html5 5.8.0 into their development pipelines, content management systems, or automated HTML processing tools may experience degraded performance or service interruptions due to memory exhaustion caused by the leak. This could affect web hosting providers, digital agencies, and enterprises relying on automated HTML validation or cleanup. While the vulnerability does not directly compromise data confidentiality or integrity, prolonged exploitation could lead to denial of service conditions, impacting business continuity. Given the local attack vector, the threat is more significant in environments where multiple users have local access or where attackers can gain local footholds, such as shared hosting or development servers. The absence of known active exploits reduces immediate risk, but public disclosure increases the likelihood of future exploitation attempts. European organizations with strict uptime requirements or limited monitoring of memory usage may face operational disruptions. Additionally, sectors with high regulatory compliance demands (e.g., finance, healthcare) may be indirectly impacted if service availability is compromised.

1. Monitor memory usage closely on systems running tidy-html5 5.8.0, especially on servers processing large volumes of HTML content or running continuous integration pipelines. 2. Restrict local access to trusted users only, minimizing the risk of local exploitation. 3. Implement resource limits (e.g., cgroups on Linux) on processes invoking tidy-html5 to prevent excessive memory consumption from impacting other services. 4. Where feasible, replace or isolate the use of tidy-html5 5.8.0 in critical environments until a patched version is available. 5. Employ containerization or sandboxing techniques to limit the impact of potential memory leaks. 6. Stay updated with HTACG project releases and apply patches promptly once available. 7. Conduct regular code audits and testing on HTML processing workflows to detect abnormal resource usage early. 8. Educate local users and administrators about the vulnerability to prevent inadvertent exploitation or misuse.