CVE-2026-49975

A flaw was found in HTTP/2, affecting various web servers. A remote attacker can exploit this vulnerability by combining an HPACK compression bomb with a zero-byte flow-control window. This technique allows a small amount of data to expand into large memory allocations on the server, which are then held, leading to a denial of service (DoS) by rendering the server inaccessible.

The Apache's httpd HTTP/2 protocol implementation has a denial-of-service (DoS) vulnerability that is rated as Important. An unauthenticated remote attacker can exploit this flaw by combining HPACK compression with flow control manipulation, leading to significant server memory exhaustion and rendering the service inaccessible. This vulnerability exists in default HTTP/2 configurations.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

See the security bulletin for a detailed mitigation procedure.