What’s Vulnerable › Vulnerabilities

CVE-2016-9909

• Severity: medium (CVSS 6.1 v3.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 2.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2017-02-22 · updated 2026-06-17
• Weakness: CWE-79

Description

The serializer in html5lib before 0.99999999 might allow remote attackers to conduct cross-site scripting (XSS) attacks by leveraging mishandling of the < (less than) character in attribute values.

Affected products

• Html5Lib: through 0.99999999

References

• http://www.openwall.com/lists/oss-security/2016/12/06/5
• http://www.openwall.com/lists/oss-security/2016/12/08/8
• http://www.securityfocus.com/bid/95132
• https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7
• https://github.com/html5lib/html5lib-python/issues/11
• https://github.com/html5lib/html5lib-python/issues/12
• https://html5lib.readthedocs.io/en/latest/changes.html#b9
• http://www.openwall.com/lists/oss-security/2016/12/06/5
• http://www.openwall.com/lists/oss-security/2016/12/08/8
• http://www.securityfocus.com/bid/95132
• https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7
• https://github.com/html5lib/html5lib-python/issues/11

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