CVE-2016-6581

Advisory

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.

Affected package

Affected versions

Fixed versions

Vulnerability changelog

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.


CONFIRM:https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html: https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html
BID:92315: http://www.securityfocus.com/bid/92315

Resources

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2016-6581
• https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html
• http://www.securityfocus.com/bid/92315