CVE-2021-26540: Sanitize html Improper Input Validation Vulnerability

MODERATE
Advisory Identifier: GHSA-mjxr-4v3x-q3m4
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CVSS 5.3
CWE-20
Published
Advisory Summary

CVE-2021-26540 is a MODERATE (CVSS 5.3) improper input validation vulnerability (CWE-20: Improper Input Validation) affecting Sanitize html libraries in the npm ecosystem. The issue involves improper input validation in sanitize-html. Remediation is available by upgrading affected packages to version 2.3.2.

CVE-2021-26540 at a Glance

CVE Identifier CVE-2021-26540
GHSA Identifier GHSA-mjxr-4v3x-q3m4
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-20: Improper Input Validation
Affected Product Sanitize html
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.3

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:N/S:U/C:N/I:L/A:N).

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

How to Fix CVE-2021-26540

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

sanitize-html fixed: 2.3.2 
npm install sanitize-html@2.3.2
Verify Direct and Transitive Dependencies

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

npm ls sanitize-html

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2021-26540, inspect your project dependencies using npm:

npm ls sanitize-html

Analyze the terminal output to locate any version of Sanitize html in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.3.2), your application is affected.

Note: The npm ls sanitize-html command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-20: Improper Input Validation, where the product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. In Sanitize html, 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

Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHostnames" option when the "allowIframeRelativeUrls" is set to true, which allows attackers to bypass hostname whitelist for iframe element, related using an src value that starts with "/\\example.com".

CVE-2021-26540 Affected Sanitize html Versions

1 component(s)
Fixed Versions:
2.3.2
Product / Package Ecosystem Affected Versions Fixed Version
sanitize-html
npm/sanitize-html
npm
< 2.3.2
2.3.2

References

NVD — CVE-2021-26540 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-26540
Sanitize html Source Repository REPOSITORY
https://github.com/apostrophecms/sanitize-html/pull/460
advisory.checkmarx.net/advisory/cx-2021-43... WEB
https://advisory.checkmarx.net/advisory/CX-2021-4309
Sanitize html Source Repository REPOSITORY
https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26

Frequently Asked Questions

What is CVE-2021-26540?
CVE-2021-26540 is a security vulnerability in Sanitize html involving Improper Input Validation in sanitize-html under CWE-20: Improper Input Validation.
Which Sanitize html versions are affected?
Affected versions include releases prior to 2.3.2 across affected packages: sanitize-html.
What version fixes CVE-2021-26540?
Upgrading to 2.3.2 (or the latest patched release for your respective branch) resolves the vulnerability.
Is sanitize-html affected?
Yes, sanitize-html is affected in releases prior to 2.3.2. Upgrade your dependency to 2.3.2 or later.
What is the CVSS score of CVE-2021-26540?
CVE-2021-26540 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
What CWE is associated with CVE-2021-26540?
CVE-2021-26540 is classified under CWE-20: Improper Input Validation (The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.).
How can I check npm dependencies for CVE-2021-26540?
Run the dependency tree command: 'npm ls sanitize-html'. 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-mjxr-4v3x-q3m4",
  "modified" : "2021-03-29T23:13:11Z",
  "published" : "2021-05-06T16:10:19Z",
  "aliases" : [ "CVE-2021-26540" ],
  "summary" : "Improper Input Validation in sanitize-html",
  "details" : "Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the \"allowedIframeHostnames\" option when the \"allowIframeRelativeUrls\" is set to true, which allows attackers to bypass hostname whitelist for iframe element, related using an src value that starts with \"/\\\\example.com\".",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "sanitize-html"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.3.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-26540"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apostrophecms/sanitize-html/pull/460"
  }, {
    "type" : "WEB",
    "url" : "https://advisory.checkmarx.net/advisory/CX-2021-4309"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#232-2021-01-26"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-03-29T23:13:11Z",
    "nvd_published_at" : "2021-02-08T17:15:00Z"
  }
}