high
7.8
CWE
399
Advisory Published
Advisory Published
Updated

CVE-2016-6581

First published: Tue Jan 10 2017(Updated: )

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.

Credit: cve@mitre.org cve@mitre.org

Affected SoftwareAffected VersionHow to fix
pip/hpack>=1.0.0<2.3.0
2.3.0
Python HPACK=1.0
Python HPACK=2.0
Python HPACK=2.0.1
Python HPACK=2.1.1
Python HPACK=2.2
Python Hyper=0.4
Python Hyper=0.6
=1.0
=2.0
=2.0.1
=2.1.1
=2.2
=0.4
=0.6

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