CVE-2025-54500 in BIG-IP
Summary
by MITRE • 08/13/2025
An HTTP/2 implementation flaw allows a denial-of-service (DoS) that uses malformed HTTP/2 control frames in order to break the max concurrent streams limit (HTTP/2 MadeYouReset Attack).
Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
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Analysis
by VulDB Data Team • 02/04/2026
The vulnerability identified as CVE-2025-54500 represents a critical flaw in HTTP/2 protocol implementations that enables a sophisticated denial-of-service attack vector through malformed control frames. This vulnerability specifically targets the max concurrent streams limit mechanism that is fundamental to HTTP/2 connection management and flow control. The attack leverages the HTTP/2 MadeYouReset technique, where malicious actors exploit improper handling of control frames to manipulate stream limits and exhaust connection resources. The flaw resides in how implementations process and validate HTTP/2 control frames, particularly those related to stream management and connection flow control parameters. This issue affects the core operational integrity of HTTP/2 servers and clients, potentially allowing attackers to disrupt legitimate service delivery without requiring authentication or privileged access.
The technical implementation flaw stems from inadequate validation of HTTP/2 control frame parameters, specifically around the MAX_CONCURRENT_STREAMS setting and associated stream limit enforcement. When malformed control frames are processed, the implementation fails to properly enforce stream limits or may incorrectly interpret the stream count, leading to premature exhaustion of concurrent stream capacity. This behavior creates a cascading effect where legitimate connections become unable to establish new streams, effectively rendering the HTTP/2 connection unusable for normal operations. The vulnerability operates at the protocol level rather than at application logic, making it particularly dangerous as it can affect the entire HTTP/2 stack regardless of underlying application security measures. This flaw directly relates to CWE-400, which covers improper handling of resource exhaustion conditions, and specifically targets the HTTP/2 protocol's flow control mechanisms as defined in RFC 7540.
The operational impact of this vulnerability extends beyond simple service disruption to encompass broader system reliability and availability concerns. Attackers can exploit this flaw to systematically consume available stream capacity, forcing legitimate users to experience connection timeouts or service unavailability. The attack can be executed with minimal resources and does not require deep protocol knowledge, making it particularly dangerous for high-traffic web servers, load balancers, and reverse proxies that rely heavily on HTTP/2 for performance optimization. Organizations using HTTP/2 implementations that are vulnerable to this attack may experience significant degradation in service quality, increased error rates, and potential revenue loss due to service unavailability. The vulnerability can be particularly damaging in environments where HTTP/2 is used for critical infrastructure components, as it can cause cascading failures across interconnected services that depend on HTTP/2 communication.
Mitigation strategies for CVE-2025-54500 require immediate attention from system administrators and security teams responsible for HTTP/2 implementations. The primary recommendation involves implementing proper validation of HTTP/2 control frames with strict enforcement of stream limit parameters and ensuring that implementations properly handle edge cases in stream management. Organizations should deploy patches or updates from vendors that address the specific control frame validation issues, while also implementing rate limiting and connection monitoring to detect anomalous stream behavior. Network-level protections such as HTTP/2 specific firewalls or proxies can help filter malformed control frames before they reach vulnerable implementations. Additionally, implementing proper monitoring and alerting for unusual stream limit behavior, connection resets, and concurrent stream exhaustion patterns can help detect exploitation attempts. From an ATT&CK perspective, this vulnerability maps to T1499.004, which covers network denial of service attacks, and T1595.001, which involves network reconnaissance through protocol analysis, making it a significant concern for both defensive and offensive security operations.