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CVE-2016-6581

26
FAUCET Score

CVE-2016-6581 describes a denial-of-service vulnerability, known as an "HPACK Bomb," affecting HTTP/2 implementations utilizing Python HPACK library versions 1.0.0 to 2.2.0. An attacker can exploit this by sending specially crafted header fields that, upon decompression, expand to a significantly larger size (e.g., 16KB expanding to 64MB), consuming excessive resources. This vulnerability has a CVSSv3 score of 7.5 (HIGH), indicating a network-based attack with low complexity and a high impact on availability. There is no evidence of active exploitation, public exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
1.0CPE matchmatch criteria
cpe:2.3:a:python:hpack:1.0:*:*:*:*:*:*:*
2.0CPE matchmatch criteria
cpe:2.3:a:python:hpack:2.0:*:*:*:*:*:*:*
2.0.1CPE matchmatch criteria
cpe:2.3:a:python:hpack:2.0.1:*:*:*:*:*:*:*
2.1.1CPE matchmatch criteria
cpe:2.3:a:python:hpack:2.1.1:*:*:*:*:*:*:*
2.2CPE matchmatch criteria
cpe:2.3:a:python:hpack:2.2:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

7.5HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
NONE
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
3.6
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.81%
Probability of exploitation in next 30 days
EPSS Percentile
76.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-24
Model: v2026.06.15
This CVE's current EPSS score of 0.0181 is in the 58th percentile among its peer group of 51,466 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

pippatch availablevia ghsa
Product: hpackFixed in: 2.3.0

Vendor Advisories (1)

pipGHSA-ffq8-576r-v26ghigh

HPACK Denial of Service vulnerability (HPACK Bomb)

Jul 5, 2019

References

python-hyper.org / hpack/en/latest/security/CVE-2016-6581.html
MitigationVendor Advisory
securityfocus.com / bid/92315
Third Party AdvisoryVDB Entry