CVE-2016-9910: Html5lib Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-8f6m-gfq9-g33v
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CVSS 6.1
CWE-79
Published
Advisory Summary

CVE-2016-9910 is a MODERATE (CVSS 6.1) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Html5lib libraries in the PyPI ecosystem. The issue involves cross-site scripting in html5lib. Remediation is available by upgrading affected packages to version 0.99999999.

CVE-2016-9910 at a Glance

CVE Identifier CVE-2016-9910
GHSA Identifier GHSA-8f6m-gfq9-g33v
Severity MODERATE
CVSS v3.1 Base Score 6.1
CWE Classification CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Affected Product Html5lib
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 6.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Changed (S:C)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2016-9910

To remediate this vulnerability, upgrade all affected Html5lib dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

html5lib fixed: 0.99999999 
pip install html5lib>=0.99999999
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show html5lib

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2016-9910, inspect your installed packages using pip:

pip show html5lib

Analyze the terminal output to locate any version of Html5lib in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.99999999), your application is affected.

Note: The pip show html5lib command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'), where the product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. In Html5lib, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

The serializer in html5lib before 0.99999999 might allow remote attackers to conduct cross-site scripting (XSS) attacks by leveraging mishandling of special characters in attribute values, a different vulnerability than CVE-2016-9909.

CVE-2016-9910 Affected Html5lib Versions

1 component(s)
Fixed Versions:
0.99999999
Product / Package Ecosystem Affected Versions Fixed Version
html5lib
pypi/html5lib
PyPI
< 0.99999999
0.99999999

References

NVD — CVE-2016-9910 NVD
https://nvd.nist.gov/vuln/detail/CVE-2016-9910
Html5lib Source Repository REPOSITORY
https://github.com/html5lib/html5lib-python/issues/11
Html5lib Source Repository REPOSITORY
https://github.com/html5lib/html5lib-python/issues/12
Security Fix Commit FIX COMMIT
https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-8f6m-gfq9-g33v
Html5lib Source Repository REPOSITORY
https://github.com/html5lib/html5lib-python
Html5lib Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/html5lib/PYSEC-2017-15.yaml
Html5lib Security Information SECURITY
https://html5lib.readthedocs.io/en/latest/changes.html#b9
Html5lib Security Information SECURITY
https://web.archive.org/web/20200514233128/http://www.securityfocus.com/bid/95132
Html5lib Security Information SECURITY
http://www.openwall.com/lists/oss-security/2016/12/06/5
Html5lib Security Information SECURITY
http://www.openwall.com/lists/oss-security/2016/12/08/8

Frequently Asked Questions

What is CVE-2016-9910?
CVE-2016-9910 is a security vulnerability in Html5lib involving Cross-site Scripting in html5lib under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Html5lib versions are affected?
Affected versions include releases prior to 0.99999999 across affected packages: html5lib.
What version fixes CVE-2016-9910?
Upgrading to 0.99999999 (or the latest patched release for your respective branch) resolves the vulnerability.
Is html5lib affected?
Yes, html5lib is affected in releases prior to 0.99999999. Upgrade your dependency to 0.99999999 or later.
What is the CVSS score of CVE-2016-9910?
CVE-2016-9910 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2016-9910?
CVE-2016-9910 is classified under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.).
How can I check PyPI dependencies for CVE-2016-9910?
Run the dependency tree command: 'pip show html5lib'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-8f6m-gfq9-g33v",
  "modified" : "2024-09-23T17:05:09Z",
  "published" : "2022-05-17T02:57:57Z",
  "aliases" : [ "CVE-2016-9910" ],
  "summary" : "Cross-site Scripting in html5lib",
  "details" : "The serializer in html5lib before 0.99999999 might allow remote attackers to conduct cross-site scripting (XSS) attacks by leveraging mishandling of special characters in attribute values, a different vulnerability than CVE-2016-9909.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "html5lib"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.99999999"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2016-9910"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/html5lib/html5lib-python/issues/11"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/html5lib/html5lib-python/issues/12"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-8f6m-gfq9-g33v"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/html5lib/html5lib-python"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/html5lib/PYSEC-2017-15.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://html5lib.readthedocs.io/en/latest/changes.html#b9"
  }, {
    "type" : "WEB",
    "url" : "https://web.archive.org/web/20200514233128/http://www.securityfocus.com/bid/95132"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2016/12/06/5"
  }, {
    "type" : "WEB",
    "url" : "http://www.openwall.com/lists/oss-security/2016/12/08/8"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-06-02T21:03:05Z",
    "nvd_published_at" : "2017-02-22T16:59:00Z"
  }
}