7.5
HIGH
CVE-2016-6581
Apache Python HPACK HTTP2 Denial of Service Vulnerability
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.

INFO

Published Date :

Jan. 10, 2017, 3:59 p.m.

Last Modified :

Jan. 27, 2017, 7:41 p.m.

Remotely Exploitable :

Yes !

Impact Score :

3.6

Exploitability Score :

3.9
Affected Products

The following products are affected by CVE-2016-6581 vulnerability. Even if cvefeed.io is aware of the exact versions of the products that are affected, the information is not represented in the table below.

ID Vendor Product Action
1 Python python
2 Python hpack
3 Python hyper
References to Advisories, Solutions, and Tools

Here, you will find a curated list of external links that provide in-depth information, practical solutions, and valuable tools related to CVE-2016-6581.

URL Resource
http://www.securityfocus.com/bid/92315 Third Party Advisory VDB Entry
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html Mitigation Vendor Advisory

We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).

Results are limited to the first 15 repositories due to potential performance issues.

The following list is the news that have been mention CVE-2016-6581 vulnerability anywhere in the article.

The following table lists the changes that have been made to the CVE-2016-6581 vulnerability over time.

Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.

  • CVE Modified by [email protected]

    May. 14, 2024

    Action Type Old Value New Value
  • Modified Analysis by [email protected]

    Jan. 27, 2017

    Action Type Old Value New Value
    Changed CPE Configuration OR *cpe:2.3:a:python_software_foundation:hpack:1.0:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.0:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.0.1:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.1.1:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.2:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hyper:0.4:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hyper:0.6:*:*:*:*:*:*:* OR *cpe:2.3:a:python:hpack:1.0:*:*:*:*:*:*:* *cpe:2.3:a:python:hpack:2.0:*:*:*:*:*:*:* *cpe:2.3:a:python:hpack:2.0.1:*:*:*:*:*:*:* *cpe:2.3:a:python:hpack:2.1.1:*:*:*:*:*:*:* *cpe:2.3:a:python:hpack:2.2:*:*:*:*:*:*:* *cpe:2.3:a:python:hyper:0.4:*:*:*:*:*:*:* *cpe:2.3:a:python:hyper:0.6:*:*:*:*:*:*:*
  • CVE Modified by [email protected]

    Jan. 13, 2017

    Action Type Old Value New Value
    Changed Description A HTTP/2 implementation built using any version of the Python HPACK library between v1.0.0 and v2.2.0 could be targetted 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. 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.
  • Initial Analysis by [email protected]

    Jan. 11, 2017

    Action Type Old Value New Value
    Added CVSS V2 (AV:N/AC:L/Au:N/C:N/I:N/A:C)
    Added CVSS V3 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
    Changed Reference Type http://www.securityfocus.com/bid/92315 No Types Assigned http://www.securityfocus.com/bid/92315 Third Party Advisory, VDB Entry
    Changed Reference Type https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html No Types Assigned https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html Mitigation, Vendor Advisory
    Added CWE CWE-399
    Added CPE Configuration OR *cpe:2.3:a:python_software_foundation:hpack:1.0:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.0:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.0.1:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.1.1:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hpack:2.2:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hyper:0.4:*:*:*:*:*:*:* *cpe:2.3:a:python_software_foundation:hyper:0.6:*:*:*:*:*:*:*
EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days. Following chart shows the EPSS score history of the vulnerability.
CWE - Common Weakness Enumeration

While CVE identifies specific instances of vulnerabilities, CWE categorizes the common flaws or weaknesses that can lead to vulnerabilities. CVE-2016-6581 is associated with the following CWEs:

Common Attack Pattern Enumeration and Classification (CAPEC)

Common Attack Pattern Enumeration and Classification (CAPEC) stores attack patterns, which are descriptions of the common attributes and approaches employed by adversaries to exploit the CVE-2016-6581 weaknesses.

Exploit Prediction

EPSS is a daily estimate of the probability of exploitation activity being observed over the next 30 days.

0.10 }} 0.00%

score

0.38726

percentile

CVSS30 - Vulnerability Scoring System
Attack Vector
Attack Complexity
Privileges Required
User Interaction
Scope
Confidentiality
Integrity
Availability