CVE-2016-6581

HighCVSS 7.5/10Last modified Jun 17, 2026

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.

Metrics

CVSS 3.0 7.5/10CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness enumeration

CWE-399

Affected software

Vendor	Product	Versions
n/a	n/a	n/a

References

http://www.securityfocus.com/bid/92315Third Party Advisory, VDB Entry
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.htmlMitigation, Vendor Advisory
http://www.securityfocus.com/bid/92315Third Party Advisory, VDB Entry
https://python-hyper.org/hpack/en/latest/security/CVE-2016-6581.htmlMitigation, Vendor Advisory

Timeline

Published: Jan 10, 2017
Last modified: Jun 17, 2026
NVD status: Modified

Related CVEs from 2016

CVE-2016-65829.1The Doorkeeper gem before 4.2.0 for Ruby might allow remote attackers to conduct replay attacks or revoke arbitrary tokens by leveraging fai CVE-2016-65855.3A Denial of Service vulnerability exists in Symantec Norton Mobile Security for Android prior to 3.16, which could let a remote malicious us CVE-2016-65863.7A security bypass vulnerability exists in Symantec Norton Mobile Security for Android before 3.16, which could let a malicious user conduct CVE-2016-65875.5An Information Disclosure vulnerability exists in the mid.dat file stored on the SD card in Symantec Norton Mobile Security for Android befo CVE-2016-65885.4A Cross-Site Scripting (XSS) vulnerability exists in the ITMS workflow process manager console in Symantec IT Management Suite 8.0.CVE-2016-65896.5A Denial of Service vulnerability exists in the ITMS workflow process manager login window in Symantec IT Management Suite 8.0.CVE-2016-65907.8A privilege escalation vulnerability exists when loading DLLs during boot up and reboot in Symantec IT Management Suite 8.0 prior to 8.0 HF4 CVE-2016-65917.1A security bypass vulnerability exists in Symantec Norton App Lock 1.0.3.186 and earlier if application pinning is enabled, which could let CVE-2016-65927.8A vulnerability was found in Symantec Norton Download Manager versions prior to 5.6. A remote user can create a specially crafted DLL file t CVE-2016-65937.8A code-execution vulnerability exists during startup in jhi.dll and otpiha.dll in Symantec VIP Access Desktop before 2.2.2, which could let CVE-2016-65947.5Blue Coat Advanced Secure Gateway 6.6, CacheFlow 3.4, ProxySG 6.5 and 6.6 allows remote attackers to bypass blocked requests, user authentic CVE-2016-65956.5The SwarmKit toolkit 1.12.0 for Docker allows remote authenticated users to cause a denial of service (prevention of cluster joins) via a lo