CVE-2016-6581

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.

Category

7.5
CVSS
Severity: High
CVSS 3.0 •
CVSS 2.0 •
EPSS 0.37%
Vendor Advisory python-hyper.org
Affected: n/a n/a
Published at:
Updated at:

References

Link Tags
http://www.securityfocus.com/bid/92315 vdb entry third party advisory
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html mitigation vendor advisory

Frequently Asked Questions

What is the severity of CVE-2016-6581?
CVE-2016-6581 has been scored as a high severity vulnerability.
How to fix CVE-2016-6581?
To fix CVE-2016-6581, make sure you are using an up-to-date version of the affected component(s) by checking the vendor release notes. As for now, there are no other specific guidelines available.
Is CVE-2016-6581 being actively exploited in the wild?
As for now, there are no information to confirm that CVE-2016-6581 is being actively exploited. According to its EPSS score, there is a ~0% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
This platform uses data from the NIST NVD, MITRE CVE, MITRE CWE, First.org and CISA KEV but is not endorsed or certified by these entities. CVE is a registred trademark of the MITRE Corporation and the authoritative source of CVE content is MITRE's CVE web site. CWE is a registred trademark of the MITRE Corporation and the authoritative source of CWE content is MITRE's CWE web site.
© 2025 Under My Watch. All Rights Reserved.