CVE-2025-11679 is an out-of-bounds read vulnerability classified under CWE-125 found in the warmcat libwebsockets library version 4.0. The flaw exists in the function lws_upng_emit_next_line, which processes PNG images when the library is compiled with the LWS_WITH_UPNG flag enabled and the HTML display stack is active. Specifically, when a user visits a website controlled by an attacker that serves a specially crafted PNG file with an unusually large height dimension, the function reads beyond the bounds of a heap-allocated buffer. This memory access violation can cause the application using libwebsockets to crash, resulting in a denial of service condition. The vulnerability does not appear to allow direct code execution or data leakage but poses a risk to availability. Exploitation requires no privileges but does require user interaction (visiting the malicious site). The CVSS 4.0 vector indicates network attack vector, high attack complexity, partial attack prerequisites, no privileges required, user interaction needed, no confidentiality or integrity impact, but high availability impact. No public exploits or patches are currently available, but users are advised to monitor for updates. The vulnerability affects version 4.0 of libwebsockets, a widely used C library for lightweight websocket and web server implementations, often embedded in IoT devices, network appliances, and web applications.

For European organizations, the primary impact of CVE-2025-11679 is the potential for denial of service in applications or devices using the vulnerable libwebsockets configuration. This can disrupt web services, IoT device functionality, or embedded system operations, particularly in sectors relying on real-time communication or web-based interfaces. Critical infrastructure operators, telecommunications providers, and industrial control systems that embed libwebsockets could experience service interruptions. While no direct data breach or code execution is indicated, repeated exploitation could degrade service availability and user trust. The requirement for user interaction limits automated widespread exploitation but targeted phishing or malicious web content delivery could still impact end users. European organizations with extensive web-facing applications or embedded devices using libwebsockets should assess exposure and potential operational impacts.

1. Disable the LWS_WITH_UPNG flag during compilation if PNG processing via libwebsockets is not required, thereby eliminating the vulnerable code path. 2. Monitor the official warmcat libwebsockets repository and security advisories for patches addressing CVE-2025-11679 and apply them promptly once available. 3. Implement web content filtering and URL reputation services to block access to untrusted or suspicious websites that could host malicious PNG files. 4. Employ runtime application monitoring to detect abnormal crashes or memory errors in applications using libwebsockets, enabling rapid incident response. 5. For embedded or IoT devices, coordinate firmware updates that include patched libwebsockets versions and ensure secure update mechanisms. 6. Conduct security reviews of web-facing applications using libwebsockets to identify and isolate vulnerable components. 7. Educate users about the risks of visiting untrusted websites and the importance of cautious web browsing to reduce user interaction risk.