CVE-2016-9909
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.
Does this matter?
Lower severity and a low EPSS score (2.16%). Track it; it rarely justifies an emergency change on its own.
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.
- CVSS 3.0
- 6.1 MEDIUMCVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- EPSS
- 2.16% probability · 82th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-79
- Affected
- html5lib/html5lib
- Source
- secalert@redhat.com
EPSS 2.2% since 27 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- http://www.openwall.com/lists/oss-security/2016/12/06/5Mailing List, Patch, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2016/12/08/8Mailing List, Patch, Third Party Advisory
- http://www.securityfocus.com/bid/95132Third Party Advisory, VDB Entry
- https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7Patch
- https://github.com/html5lib/html5lib-python/issues/11Vendor Advisory
- https://github.com/html5lib/html5lib-python/issues/12Vendor Advisory
- https://html5lib.readthedocs.io/en/latest/changes.html#b9Release Notes
- http://www.openwall.com/lists/oss-security/2016/12/06/5Mailing List, Patch, Third Party Advisory
- http://www.openwall.com/lists/oss-security/2016/12/08/8Mailing List, Patch, Third Party Advisory
- http://www.securityfocus.com/bid/95132Third Party Advisory, VDB Entry
- https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7Patch
- https://github.com/html5lib/html5lib-python/issues/11Vendor Advisory
- https://github.com/html5lib/html5lib-python/issues/12Vendor Advisory
- https://html5lib.readthedocs.io/en/latest/changes.html#b9Release Notes
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.