CVE-2021-29272: Github.com/microcosm cc/bluemonday Cross-Site Scripting Vulnerability

MODERATE
Advisory Identifier: GHSA-3x58-xr87-2fcj
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CVSS 6.1
CWE-79
Published
Advisory Summary

CVE-2021-29272 is a MODERATE (CVSS 6.1) cross-site scripting vulnerability (CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')) affecting Github.com/microcosm cc/bluemonday libraries in the Go ecosystem. The issue involves cross-site scripting in bluemonday. Remediation is available by upgrading affected packages to version 1.0.5.

CVE-2021-29272 at a Glance

CVE Identifier CVE-2021-29272
GHSA Identifier GHSA-3x58-xr87-2fcj
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 Github.com/microcosm cc/bluemonday
Package Ecosystem Go
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:3.1/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-2021-29272

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

github.com/microcosm-cc/bluemonday fixed: 1.0.5 
Upgrade github.com/microcosm-cc/bluemonday to 1.0.5
Verify Direct and Transitive Dependencies

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

inspect dependencies for github.com/microcosm-cc/bluemonday

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-29272, inspect your project dependencies for Github.com/microcosm cc/bluemonday:

inspect dependencies for github.com/microcosm-cc/bluemonday

Analyze the terminal output to locate any version of Github.com/microcosm cc/bluemonday in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.0.5), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

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 Github.com/microcosm cc/bluemonday, 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

bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the "script" string.

CVE-2021-29272 Affected Github.com/microcosm cc/bluemonday Versions

1 component(s)
Fixed Versions:
1.0.5
Product / Package Ecosystem Affected Versions Fixed Version
github.com/microcosm-cc/bluemonday
golang/github.com/microcosm-cc/bluemonday
Go
< 1.0.5
1.0.5

References

NVD — CVE-2021-29272 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-29272
Github.com/microcosm cc/bluemonday Source Repository REPOSITORY
https://github.com/microcosm-cc/bluemonday/issues/111
Security Fix Commit FIX COMMIT
https://github.com/microcosm-cc/bluemonday/commit/524f142fe46e945b7dcd291d7805c4b7dcf75bee
Github.com/microcosm cc/bluemonday Source Repository REPOSITORY
https://github.com/microcosm-cc/bluemonday
Github.com/microcosm cc/bluemonday Release RELEASE
https://github.com/microcosm-cc/bluemonday/releases/tag/v1.0.5
pkg.go.dev/vuln/go-2022-0762 WEB
https://pkg.go.dev/vuln/GO-2022-0762
vuln.ryotak.me/advisories/4 WEB
https://vuln.ryotak.me/advisories/4
vuln.ryotak.me/advisories/4.txt WEB
https://vuln.ryotak.me/advisories/4.txt

Frequently Asked Questions

What is CVE-2021-29272?
CVE-2021-29272 is a security vulnerability in Github.com/microcosm cc/bluemonday involving Cross-site scripting in bluemonday under CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting').
Which Github.com/microcosm cc/bluemonday versions are affected?
Affected versions include releases prior to 1.0.5 across affected packages: github.com/microcosm-cc/bluemonday.
What version fixes CVE-2021-29272?
Upgrading to 1.0.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is github.com/microcosm-cc/bluemonday affected?
Yes, github.com/microcosm-cc/bluemonday is affected in releases prior to 1.0.5. Upgrade your dependency to 1.0.5 or later.
What is the CVSS score of CVE-2021-29272?
CVE-2021-29272 has a CVSS v3.1 base score of 6.1 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
What CWE is associated with CVE-2021-29272?
CVE-2021-29272 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 Go dependencies for CVE-2021-29272?
Run the dependency tree command: 'inspect dependencies for github.com/microcosm-cc/bluemonday'. 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-3x58-xr87-2fcj",
  "modified" : "2024-05-20T21:19:56Z",
  "published" : "2021-05-18T21:07:37Z",
  "aliases" : [ "CVE-2021-29272" ],
  "summary" : "Cross-site scripting in bluemonday",
  "details" : "bluemonday before 1.0.5 allows XSS because certain Go lowercasing converts an uppercase Cyrillic character, defeating a protection mechanism against the \"script\" string.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/microcosm-cc/bluemonday"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.0.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-29272"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microcosm-cc/bluemonday/issues/111"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microcosm-cc/bluemonday/commit/524f142fe46e945b7dcd291d7805c4b7dcf75bee"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/microcosm-cc/bluemonday"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/microcosm-cc/bluemonday/releases/tag/v1.0.5"
  }, {
    "type" : "WEB",
    "url" : "https://pkg.go.dev/vuln/GO-2022-0762"
  }, {
    "type" : "WEB",
    "url" : "https://vuln.ryotak.me/advisories/4"
  }, {
    "type" : "WEB",
    "url" : "https://vuln.ryotak.me/advisories/4.txt"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-05-18T21:05:51Z",
    "nvd_published_at" : null
  }
}