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CVE-2021-26539

18
FAUCET Score

CVE-2021-26539 is a medium-severity vulnerability affecting Apostrophe Technologies' sanitize-html library prior to version 2.3.1. It allows an attacker to bypass hostname whitelist validation, specifically the "allowedIframeHostnames" option, by exploiting improper handling of internationalized domain names (IDNs). The vulnerability has a CVSS score of 5.3, indicating a network-based attack with low complexity and a potential impact on integrity, but no confidentiality or availability. There is no evidence of active exploitation, public exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 2.3.1CPE matchmatch criteria
cpe:2.3:a:apostrophecms:sanitize-html:*:*:*:*:*:node.js:*:*

CVSS Data

CVSS version used by this source: 3.1

5.3MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.95%
Probability of exploitation in next 30 days
EPSS Percentile
78.2%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0195 is in the 66th percentile among its peer group of 23,701 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (6)

github_advisorypatch availablevia nvd_reference
View patch
npmpatch availablevia ghsa
Product: sanitize-htmlFixed in: 2.3.1
redhatpatch availablevia redhat_api
Product: Red Hat OpenShift Container Platform 4.7Fixed in: openshift4/ose-console:v4.7.0-202102130115.p0
View patch
redhatpatch availablevia redhat_api
Product: Red Hat OpenShift Container Platform 4.8Fixed in: openshift4/ose-thanos-rhel8:v4.8.0-202106291913.p0.git.c358e96.assembly.stream
View patch
redhatpatch availablevia redhat_api
Product: Red Hat OpenShift Container Platform 4.9Fixed in: openshift4/ose-prometheus:v4.9.0-202109302016.p0.git.3197fa7.assembly.stream
View patch
redhatno patchvia redhat_api
Product: OpenShift Service Mesh 2.0Fixed in: servicemesh-prometheus

Vendor Advisories (2)

npmGHSA-rjqq-98f6-6j3rmedium

Improper Input Validation in sanitize-html

May 6, 2021
redhatCVE-2021-26539Moderate

sanitize-html: improper handling of internationalized domain name (IDN) can lead to bypass hostname whitelist validation

Jan 22, 2021

References

advisory.checkmarx.net / advisory/CX-2021-4308
ExploitThird Party Advisory
github.com / apostrophecms/sanitize-html/blob/main/CHANGELOG.md
Release NotesThird Party Advisory
github.com / apostrophecms/sanitize-html/pull/458
PatchThird Party Advisory