CVE-2016-6581: python hpack Resource Management Errors
Vulnerability summary
CVE-2016-6581 is a high (CVSS 7.8) Resource Management Errors vulnerability in python hpack. EPSS estimates a 1.83% chance of exploitation in the next 30 days, higher than 78.4% of scored vulnerabilities.
Advisory lineage
Upstream 0 · Downstream 1 · Related 1Timeline
- 10-01-2017PublishedVulnerability first disclosed.
- 06-08-2024Last modifiedVulnerability information updated.
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.
CVSS metrics
6 scores · 4 sources · 4 versions- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated7.5HighCVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
1.83%
Chance of exploitation in the next 30 days
Percentile
78%
Versus all other CVEs
30-day change
0.00 pp
From 1.83% on 18-09-2026
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Debian1 product
- python-hpack< 2.3.0-1
Opensuse1 product
- python-hpack&distro=openSUSE Tumbleweed< 4.0.0-2.7
PyPI1 product
- hpack≥ 1.0.0, < 2.3.0 | < 2.3.0
Ubuntu1 product
- python-hpackAll versions (No fix recorded)
5 vendors · 6 products
References
14 links- python-hyper.org/hpack/en/latest/security/CVE-2016-6581.htmlX Refsource CONFIRMMitigationVendor AdvisoryWEB
