CVE-2025-6273 is a medium-severity vulnerability identified in the WebAssembly Binary Toolkit (wabt) versions 1.0.0 through 1.0.37. The vulnerability is located in the LogOpcode function within the src/binary-reader-objdump.cc source file. Specifically, it involves a reachable assertion condition, which means that under certain manipulated inputs, the program can trigger an assertion failure. This can lead to abnormal termination or denial of service of the affected component. The vulnerability requires local access with low privileges (local access with low privileges) and does not require user interaction or authentication. The exploitability is considered low complexity, but the impact is limited to local denial of service rather than remote code execution or data compromise. The vulnerability's real-world impact is somewhat uncertain, as the maintainer has indicated that typical WebAssembly programs may not trigger this assertion, suggesting limited practical exploitation scenarios. No public exploits are currently known in the wild, although the vulnerability details have been disclosed publicly. The CVSS 4.0 vector indicates a base score of 4.8, reflecting a medium severity primarily due to the local attack vector and limited impact on confidentiality, integrity, and availability. The vulnerability affects a widely used open-source toolkit for WebAssembly binary processing, which is often employed in development, debugging, and analysis environments rather than production runtime environments.

For European organizations, the impact of this vulnerability is expected to be limited but non-negligible in specific contexts. Organizations involved in software development, WebAssembly module analysis, or tooling that incorporates wabt could experience local denial of service conditions if an attacker with local access exploits this vulnerability. This could disrupt development workflows or automated build and analysis pipelines. However, since the vulnerability requires local access and does not affect remote execution or compromise data confidentiality or integrity, the risk to critical infrastructure or sensitive data is low. The uncertainty about real-world exploitability further reduces the immediate threat level. Nonetheless, organizations relying on wabt for security-sensitive WebAssembly analysis or embedded in larger toolchains should consider the potential for disruption and the need for patching to maintain operational stability and security hygiene.

Update wabt to a version later than 1.0.37 once a patch is released or confirmed by the maintainers to address this assertion issue. Restrict local access to systems running wabt, especially in shared or multi-user environments, to prevent unauthorized users from triggering the vulnerability. Implement strict access controls and monitoring on developer workstations and build servers where wabt is used to detect unusual crashes or assertion failures. Incorporate fuzz testing and input validation in WebAssembly processing workflows to detect malformed or malicious wasm binaries that could trigger assertions. Consider isolating the execution environment of wabt (e.g., using containers or sandboxing) to limit the impact of potential denial of service conditions. Engage with the wabt community or maintainers to track updates and confirm the applicability of the vulnerability to your specific use cases and wasm workloads.