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.
Published 2017-01-10 15:59:00
Updated 2017-01-27 19:41:37
Source MITRE
View at NVD,   CVE.org
Vulnerability category: Denial of service

Exploit prediction scoring system (EPSS) score for CVE-2016-6581

0.10%
Probability of exploitation activity in the next 30 days EPSS Score History
~ 39 %
Percentile, the proportion of vulnerabilities that are scored at or less

CVSS scores for CVE-2016-6581

Base Score Base Severity CVSS Vector Exploitability Score Impact Score Score Source First Seen
7.8
HIGH AV:N/AC:L/Au:N/C:N/I:N/A:C
10.0
6.9
NIST
7.5
HIGH CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.9
3.6
NIST

CWE ids for CVE-2016-6581

  • Assigned by: nvd@nist.gov (Primary)

References for CVE-2016-6581

Products affected by CVE-2016-6581

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