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.
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.018 (78.0th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 78th percentile — 78.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.018 · newest: 0.018 · change: 0.000
Affected products
- Python Hpack — versions 1.0, 2.0, 2.0.1
- Python Hyper — versions 0.4, 0.6
Weakness classification (CWE)
References
- www.securityfocus.com/bid/92315 (VDB Entry, Third Party Advisory, vdb-entry)
- python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html (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.