Vulnerability Details CVE-2016-6581
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 41.8%
CVSS Severity
CVSS v3 Score 7.5
CVSS v2 Score 7.8
Products affected by CVE-2016-6581
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cpe:2.3:a:python:hpack:1.0
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cpe:2.3:a:python:hpack:2.0
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cpe:2.3:a:python:hpack:2.0.1
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cpe:2.3:a:python:hpack:2.1.1
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cpe:2.3:a:python:hpack:2.2
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cpe:2.3:a:python:hyper:0.4
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cpe:2.3:a:python:hyper:0.6