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CVE-2016-6581

Published: Jan 10, 2017Updated: May 6, 2026 Sources: CVE List NVD GHSA BDUCWE-399
NVD MITRE
7.5CVSSHIGH
EPSS Score
1.8%
Top 25.0%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

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 Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
Open in CVSS calculator →

Weaknesses

CWE-399

Affected Products

n/an/a
hpackPyPIOSS Libraries
hpackpythonOSS Libraries
hyperpythonOSS Libraries
hpackСообщество свободного программного обеспечения
On-prem
Operating Systems / linux-distro
pypipackage-ecosystemOSS Libraries
pythonoss-projectUSOSS Libraries
сообщество свободного программного обеспеченияoss-projectOperating Systemsaka сообщество свободного программного обеспечения, fsf

Exploitability

Official Patch Available
Workaround Available

References

http://www.securityfocus.com/bid/92315
securityfocus.com
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.html
python-hyper.org
https://nvd.nist.gov/vuln/detail/CVE-2016-6581
nvd.nist.gov
and 6 more references View all →

Timeline

Published
Jan 10, 2017
Last Updated
May 6, 2026
News mentions
1

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