What is CVE-2016-6581?

CVE-2016-6581 is a high-severity vulnerability in Python Hpack, classified under CWE-399. CVSS score: 7.5/10. Published 2017-01-10.

How severe is CVE-2016-6581?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Python Hpack

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.

EPSS: 0.018 (76.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Python Hpack — versions 1.0, 2.0, 2.0.1
Python Hyper — versions 0.4, 0.6
N/a — versions n/a

Weakness classification (CWE)

CWE-399

References

cve@mitre.org (VDB Entry, Third Party Advisory, vdb-entry, x_refsource_BID)
cve@mitre.org (x_refsource_CONFIRM, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2016-6581?: CVE-2016-6581 is a high-severity vulnerability in Python Hpack, classified under CWE-399. CVSS score: 7.5/10. Published 2017-01-10.
How severe is CVE-2016-6581?: High severity. CVSS v3 base score is 7.5 out of 10.