CVE-2025-62504 is a use-after-free vulnerability (CWE-416) identified in the Envoy open source edge and service proxy, specifically within its Lua filter component. Envoy versions earlier than 1.36.2, 1.35.6, 1.34.10, and 1.33.12 are affected. The vulnerability manifests when a Lua script executing during the response phase rewrites the response body such that its size exceeds the configured per_connection_buffer_limit_bytes, which defaults to 1MB. Under these conditions, Envoy generates a local reply whose headers override the original response headers. This process leaves dangling references in memory, causing a use-after-free condition that leads to a crash of the Envoy process, resulting in denial of service (DoS). The vulnerability does not affect confidentiality or integrity but impacts availability. Exploitation requires network access and privileges to execute Lua scripts within Envoy, but no user interaction is needed. While increasing buffer limits such as per_connection_buffer_limit_bytes, initial_stream_window_size for HTTP/2, or per_request_buffer_limit_bytes can reduce the chance of triggering the flaw, these are not complete fixes. The definitive mitigation is upgrading to patched Envoy versions 1.36.2, 1.35.6, 1.34.10, or 1.33.12. No public exploits are currently known, but the vulnerability's nature and ease of triggering pose a risk to service stability in deployments using vulnerable versions.

For European organizations, the primary impact of CVE-2025-62504 is denial of service due to Envoy process crashes. Envoy is widely used in cloud-native environments, microservices architectures, and edge proxy deployments, including by telecom providers, financial institutions, and large enterprises across Europe. Service disruptions could affect critical applications, customer-facing services, and internal communications, leading to operational downtime and potential financial losses. Since the vulnerability requires privileges to run Lua scripts, insider threats or compromised components could exploit it to disrupt services. The lack of confidentiality or integrity impact limits data breach concerns, but availability degradation in high-demand environments could affect compliance with service-level agreements and regulatory requirements like GDPR if services become unavailable. Organizations relying on Envoy for load balancing, API gateways, or service mesh functions should prioritize remediation to maintain service continuity.

1. Upgrade Envoy to versions 1.36.2, 1.35.6, 1.34.10, or 1.33.12 as soon as possible to fully remediate the use-after-free vulnerability. 2. If immediate upgrade is not feasible, temporarily increase per_connection_buffer_limit_bytes and initial_stream_window_size (for HTTP/2) to reduce the likelihood of triggering the vulnerability, but do not rely on this as a permanent fix. 3. Similarly, increase per_request_buffer_limit_bytes and request_body_buffer_limit to mitigate risk. 4. Restrict and audit Lua script execution privileges within Envoy to trusted users and processes to minimize exploitation potential. 5. Monitor Envoy logs and metrics for unexpected crashes or local replies generated during response phases as indicators of attempted exploitation. 6. Implement robust incident response and recovery plans to quickly restore services if a denial of service occurs. 7. Conduct security reviews of Lua scripts modifying response bodies to ensure they do not inadvertently cause oversized responses. 8. Engage with Envoy community and security advisories for updates and patches.