{"id":"PYSEC-2017-87","details":"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.","aliases":["CVE-2016-6581","GHSA-ffq8-576r-v26g"],"modified":"2023-11-08T03:58:32.800713Z","published":"2017-01-10T15:59:00Z","references":[{"type":"WEB","url":"https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html"},{"type":"WEB","url":"http://www.securityfocus.com/bid/92315"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-ffq8-576r-v26g"}],"affected":[{"package":{"name":"hpack","ecosystem":"PyPI","purl":"pkg:pypi/hpack"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}],"versions":["1.0.0","1.0.1","1.1.0","2.0.0","2.0.1","2.1.0","2.1.1","2.2.0"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/hpack/PYSEC-2017-87.yaml"}}],"schema_version":"1.7.3"}