CVE-2016-6581

HighCVSS 7.5/10Last modified Jun 17, 2026

Description

A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targeted for a denial of service attack, specifically a so-called "HPACK Bomb" attack. This attack occurs when an attacker inserts a header field that is exactly the size of the HPACK dynamic header table into the dynamic header table. The attacker can then send a header block that is simply repeated requests to expand that field in the dynamic table. This can lead to a gigantic compression ratio of 4,096 or better, meaning that 16kB of data can decompress to 64MB of data on the target machine.

Metrics

CVSS 3.0 7.5/10CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness enumeration

CWE-399

Affected software

No affected versions have been published.

Timeline

Published: Jan 10, 2017
Last modified: Jun 17, 2026
NVD status: Modified

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