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CVE-2016-9909

17
FAUCET Score

CVE-2016-9909 describes a cross-site scripting (XSS) vulnerability in html5lib versions prior to 0.99999999, stemming from improper handling of the less than character in attribute values during serialization. This medium-severity vulnerability (CVSS 6.1) can be exploited remotely with low attack complexity, requiring user interaction, and could lead to limited confidentiality and integrity impacts. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
<= 0.99999999CPE matchmatch criteria
cpe:2.3:a:html5lib:html5lib:*:1.0b8:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

6.1MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
2.8
Impact Score
2.7
CvssVersion
3.0

Exploit Intelligence

EPSS Score
2.16%
Probability of exploitation in next 30 days
EPSS Percentile
80.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-24
Model: v2026.06.15
This CVE's current EPSS score of 0.0216 is in the 90th percentile among its peer group of 26,209 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.1 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 (2)

github_advisorypatch availablevia nvd_reference
View patch
pippatch availablevia ghsa
Product: html5libFixed in: 0.999999999

Vendor Advisories (1)

pipGHSA-v9v9-xffq-rwr4medium

Improper Neutralization of Input During Web Page Generation in html5lib

May 17, 2022

References

github.com / html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7
Patch
github.com / html5lib/html5lib-python/issues/11
Vendor Advisory
github.com / html5lib/html5lib-python/issues/12
Vendor Advisory
html5lib.readthedocs.io / en/latest/changes.html
Release Notes
openwall.com / lists/oss-security/2016/12/06/5
Mailing ListPatchThird Party Advisory
openwall.com / lists/oss-security/2016/12/08/8
Mailing ListPatchThird Party Advisory
securityfocus.com / bid/95132
Third Party AdvisoryVDB Entry