A newly discovered vulnerability in HTTP/2, known as 'MadeYouReset' and tracked as CVE-2025-8671, has raised concerns among cybersecurity experts due to its potential for enabling large-scale denial-of-service (DoS) attacks. Researchers Gal Bar Nahum, Anat Bremler-Barr, and Yaniv Harel revealed that the flaw allows attackers to bypass the standard limit of 100 concurrent HTTP/2 requests per TCP connection, significantly amplifying the risk of server overload. 'By crafting certain invalid control frames or violating protocol sequencing at just the right moment, we can make the server send RST_STREAM for a stream that already carried a valid request,' the researchers stated. The vulnerability has been confirmed to affect multiple HTTP/2 implementations, prompting the researchers to notify over 100 vendors of the flaw.
The MadeYouReset vulnerability builds upon earlier issues, particularly the Rapid Reset vulnerability (CVE-2023-44487), which also exploited weaknesses in the handling of RST_STREAM frames. This latest flaw allows attackers to send thousands of requests to a server, potentially leading to out-of-memory crashes in some vendor implementations. According to the researchers, 'the discovery of server-triggered Rapid Reset vulnerabilities highlights the evolving complexity of modern protocol abuse.' This vulnerability underscores the challenges security professionals face in managing and securing widely deployed protocols like HTTP/2, which is the backbone of much of today's web traffic.
Affected products include well-known implementations such as Apache Tomcat (CVE-2025-48989), F5 BIG-IP (CVE-2025-54500), and Netty (CVE-2025-55163). The implications of this vulnerability are significant, considering HTTP/2's widespread use since its introduction in 2012. Security experts have noted that the flaw allows for effectively unbounded concurrent work on servers, posing a serious threat to service availability.
In response to the vulnerability, many vendors are actively issuing patches and updates. Security teams are advised to review their systems for affected versions and apply necessary updates to mitigate the risk of exploitation. 'Multiple vendors have issued patches or responses to the vulnerability,' noted OSS Security, emphasizing the importance of immediate action to protect systems.
As the situation develops, cybersecurity professionals are encouraged to stay informed about updates from vendors and implement recommended security measures to safeguard against potential attacks stemming from this vulnerability. The urgency of applying patches is critical, as the potential for large-scale exploitation remains a pressing concern in the cybersecurity landscape.
