CVE-2016-6581

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.

Primary references

• cve@mitre.org — Third Party Advisory, VDB Entry
• cve@mitre.org — Mitigation, Vendor Advisory
• af854a3a-2127-422b-91ae-364da2661108 — Third Party Advisory, VDB Entry
• af854a3a-2127-422b-91ae-364da2661108 — Mitigation, Vendor Advisory