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HTTP/2 Bomb exploit chains compression and connection holds to crash web servers

Feeds.4Sysops •IT News • June 3, 2026

A newly discovered vulnerability called HTTP/2 Bomb allows remote attackers to crash major web servers by combining header compression exploits with connection-holding techniques. The attack targets the HPACK header compression scheme by sending thousands of tiny header entries that force the server to allocate significant memory for bookkeeping. By using a zero-byte flow-control window, the attacker prevents the server from ever releasing this allocated memory, effectively pinning it indefinitely. Source

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New HTTP/2 Bomb DoS Attack Crashes Major Web Servers The HTTP/2 Bomb is a newly discovered denial-of-service (DoS) attack that targets default configurations of major web servers, including NGINX, Apache, Microsoft IIS, Envoy, and Cloudflare Pingora. This attack, identified by researchers at Calif and OpenAI's Codex, exploits the HPACK header compression mechanism and employs a zero-byte flow-control window to prevent memory from being released. A single attacker can exhaust tens of gigabytes of server memory in seconds, rendering the server inaccessible. Proof-of-concept exploits have been published, and while some platforms have released patches, many remain vulnerable. The full technical details will be presented at the Real World AI Security conference later this month. 11 sources 69

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HTTP/2 Bomb exploit chains compression and connection holds to crash web servers

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Extracted Entities

Attack Types (1)

CWE Weaknesses (1)

MITRE ATT&CK (1)

Vulnerabilities (1)