CVE-2024-2653 is a vulnerability classified under CWE-789 (Memory Allocation with Excessive Size Value) affecting the AMPHP amphp/http-client library, specifically version 4.0.0-rc10. The issue arises from the way the library handles HTTP/2 CONTINUATION frames: it collects these frames in an unbounded buffer without enforcing any size limit until the END_HEADERS flag is received. This design flaw allows an attacker to send a sequence of CONTINUATION frames that cause the client to allocate an excessively large amount of memory. The result is an out-of-memory (OOM) condition that crashes the application, leading to denial of service (DoS). The vulnerability is remotely exploitable over the network without requiring authentication or user interaction, as it leverages the HTTP/2 protocol framing. The CVSS v3.1 score of 8.2 reflects the high impact on availability and the ease of exploitation. While no public exploits have been reported yet, the vulnerability poses a significant risk to services relying on this library for HTTP client functionality, especially those handling HTTP/2 traffic. The absence of patch links suggests that a fix may still be pending, emphasizing the need for immediate mitigation measures. This vulnerability could be exploited by attackers to disrupt web services, degrade user experience, or cause cascading failures in dependent systems.

For European organizations, the primary impact of CVE-2024-2653 is on service availability. Applications and services using the vulnerable amphp/http-client library for HTTP/2 communications may crash due to OOM conditions triggered by maliciously crafted HTTP/2 CONTINUATION frames. This can lead to denial of service, affecting business continuity, customer trust, and potentially causing financial losses. Organizations in sectors such as finance, e-commerce, and public services that rely on asynchronous PHP frameworks and HTTP/2 for performance and scalability are particularly at risk. Additionally, the disruption could be exploited as part of a larger attack chain to weaken defenses or distract security teams. Given the remote exploitability without authentication, attackers can target exposed services directly, increasing the threat surface. The lack of known exploits currently provides a window for proactive defense, but the high CVSS score indicates that exploitation could have severe consequences if weaponized.

1. Monitor vendor channels closely for official patches or updates addressing CVE-2024-2653 and apply them promptly once available. 2. In the interim, implement strict HTTP/2 frame size limits at the network perimeter or via reverse proxies to prevent excessive CONTINUATION frame sequences from reaching vulnerable clients. 3. Employ runtime memory usage monitoring and alerting on services using amphp/http-client to detect abnormal memory consumption patterns indicative of exploitation attempts. 4. Consider deploying Web Application Firewalls (WAFs) or HTTP/2-aware intrusion prevention systems that can detect and block malformed or suspicious HTTP/2 frames. 5. Review and restrict exposure of services using the vulnerable library to untrusted networks where possible, reducing the attack surface. 6. Conduct code audits and testing for similar unbounded buffer issues in other components to prevent analogous vulnerabilities. 7. Educate development teams on secure handling of protocol frames and memory management best practices to avoid future CWE-789 issues.