What is the CVSS score of CVE-2021-26539?

CVE-2021-26539 has a CVSS 3.1 base score of 5.3 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N. EPSS exploitation probability: 2.0%.

Is there a public PoC exploit available for CVE-2021-26539?

Yes, a public proof-of-concept exploit is available for CVE-2021-26539. Prioritise patching immediately. EPSS: 2.0%.

Is there a patch available for CVE-2021-26539?

Yes, a patch is available for CVE-2021-26539. Update the affected software to the latest version immediately.

Sanitize Html CVE-2021-26539

MEDIUM

2021-02-08 cve@mitre.org

Authentication Bypass Sanitize Html Apostrophecms

5.3

CVSS 3.1 · NVD

View

Vulnerability Assessment

Impact	CVSS score of 5.3 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.
Exploit ScenarioDerived	This vulnerability can be exploited remotely over the network. Successful exploitation could compromise the medium-severity affected system.

This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).

Patch available 2.0% exploitation probability (EPSS)

Get an e-mail when this CVE is exploited, patched or re-scored. Free account.

Alert me

AnalysisAI

Apostrophe Technologies sanitize-html before 2.3.1 does not properly handle internationalized domain name (IDN) which could allow an attacker to bypass hostname whitelist validation set by the. Rated medium severity (CVSS 5.3), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Apply vendor patches when available. Implement network segmentation and monitoring as interim mitigations.

Affected Packages

npm sanitize-html fix: 2.3.1

Source: OSV (Open Source Vulnerabilities)

Affects your stack

Affects 1 package in npm

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

Apostrophe Technologies sanitize-html before 2.3.1 does not properly handle internationalized domain name (IDN) which could allow an attacker to bypass hostname whitelist validation set by the "allowedIframeHostnames" option. Affected products include: Apostrophecms Sanitize-Html. Version information: before 2.3.1.

Know when Sanitize Html gets its next vulnerability

Watch products and get an email when something new is published
Check this CVE against your own stack and servers
Exploit and PoC references, threat intelligence from 22 sources

Continue with Google Continue with GitHub

No credit card · 7-day full trial

Severity by source

NVD PRIMARY 5.3 MEDIUM

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

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

Low

Availability

None

DescriptionNVD

Threat Intelligence Overview

EPSS Score

2.0%

Top 22% exploitable

Exploit

POC

Public exploit code exists

Data Quality

3 sources

Confidence: Low

NVD

CVE.org

EPSS

GitHub

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity MEDIUM

CISA KEV No

Public POC Yes

EPSS 2.0%

Patch available Yes

Active threat No

Deciding rule

MEDIUM severity (CVSS 4.0-6.9)

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Scheduled

Exploitation· derived

Poc

System Exposure· derived

Open

Automatable· derived

Yes

Human Impact· derived

Medium

Priority Score

Low Medium High Critical

KEV: 0

EPSS: +2

CVSS: +26

PoC: +20

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Authentication Bypass CRITICAL

Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.

Affected Products (CPE)NVD

cpe:2.3:a:apostrophecms:sanitize-html:*:*:*:*:*:node.js:*:*

More in Sanitize Html

View all

CVE-2014-125128 MEDIUM This Month POC

6.1 Sep 08

'sanitize-html' prior to version 1.0.3 is vulnerable to Cross-site Scripting (XSS). Rated medium severity (CVSS 6.1), th

CVE-2019-25225 MEDIUM This Month POC

6.1 Sep 08

`sanitize-html` prior to version 2.0.0-beta is vulnerable to Cross-site Scripting (XSS). Rated medium severity (CVSS 6.1

CVE-2024-21501 MEDIUM This Month POC

5.3 Feb 24

Versions of the package sanitize-html before 2.12.1 are vulnerable to Information Exposure when used on the backend and

CVE-2021-26540 MEDIUM This Month POC

5.3 Feb 08

Apostrophe Technologies sanitize-html before 2.3.2 does not properly validate the hostnames set by the "allowedIframeHos

CVE-2022-25887 HIGH This Week

7.5 Aug 30

The package sanitize-html before 2.7.1 are vulnerable to Regular Expression Denial of Service (ReDoS) due to insecure gl

CVE-2026-40186 MEDIUM This Month

6.1 Apr 15

Cross-site scripting (XSS) in ApostropheCMS 4.28.0 and sanitize-html 2.17.1 allows remote attackers to bypass HTML tag f

CVE-2026-113661 MEDIUM This Month

5.4 Oct 20

Stored cross-site scripting can occur in sites using sanitize-html before 2.18.0 when a non-default allow-list permits m

CVE-2026-53606 MEDIUM This Month

5.4 Jun 12

Cross-site scripting in sanitize-html prior to 2.17.5 allows low-privileged attackers to inject executable `javascript:`

CVE-2026-113654 MEDIUM This Month

5.3 Oct 20

Stored cross-site scripting in sanitize-html before 2.18.0 occurs only when the sanitizer is configured with a non-defau

CVE-2026-113650 MEDIUM This Month

5.3 Oct 20

Unbounded recursive re-sanitization in sanitize-html 2.18.0 allows remote attackers to exhaust the Node.js call stack an

CVE-2026-113657 LOW Monitor

3.7 Oct 20

sanitize-html 2.17.7 and later before 2.18.0 can bypass SMIL URL protection when an application opts into a non-default

Same technique Authentication Bypass

View all

CVE-2015-3306 CRITICAL POC

10.0

CVE-2023-22515 CRITICAL POC

9.8

CVE-2012-4681 CRITICAL POC

9.8

CVE-2013-2465 CRITICAL POC

9.8

CVE-2011-3544 CRITICAL POC

9.8

CVE-2022-40684 CRITICAL POC

9.8

CVE-2025-61882 CRITICAL POC

9.8

CVE-2024-0012 CRITICAL POC

9.3

References

Advisories & patches

PATCH https://github.com/apostrophecms/sanitize-html/pull/458 REF https://github.com/apostrophecms/sanitize-html/blob/main/CHANGELOG.md#231-2021-01-22

Search Externally

GitHub PoC

Exploit-DB PacketStorm Snyk Rapid7 Nuclei Templates Trickest PoC

Back