CVE-2016-6581

7.5 HIGH
Published: January 10, 2017 Modified: May 06, 2026
View on NVD

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
http://www.securityfocus.com/bid/92315
Source: cve@mitre.org
Third Party Advisory VDB Entry
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html
Source: cve@mitre.org
Mitigation Vendor Advisory
http://www.securityfocus.com/bid/92315
Source: af854a3a-2127-422b-91ae-364da2661108
Third Party Advisory VDB Entry
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html
Source: af854a3a-2127-422b-91ae-364da2661108
Mitigation Vendor Advisory

4 reference(s) from NVD

Quick Stats

CVSS v3 Score
7.5 / 10.0
EPSS (Exploit Probability)
0.4%
60th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

python