VDB-354636 · CVE-2026-21631 · GCVE-0-2026-21631

Joomla CMS up to 5.4.3/6.0.3 Multilingual Associations cross site scripting

CVSS Meta Temp Score CVSS is a standardized scoring system to determine possibilities of attacks. The Temp Score considers temporal factors like disclosure, exploit and countermeasures. The unique Meta Score calculates the average score of different sources to provide a normalized scoring system.	Current Exploit Price (≈) Our analysts are monitoring exploit markets and are in contact with vulnerability brokers. The range indicates the observed or calculated exploit price to be seen on exploit markets. A good indicator to understand the monetary effort required for and the popularity of an attack.	CTI Interest Score Our Cyber Threat Intelligence team is monitoring different web sites, mailing lists, exploit markets and social media networks. The CTI Interest Score identifies the interest of attackers and the security community for this specific vulnerability in real-time. A high score indicates an elevated risk to be targeted for this vulnerability.
2.4	$0-$5k	0.00

Summaryinfo

A vulnerability, which was classified as problematic, was found in Joomla CMS up to 5.4.3/6.0.3. The impacted element is an unknown function of the component Multilingual Associations. The manipulation results in cross site scripting. This vulnerability is identified as CVE-2026-21631. The attack can be executed remotely. There is not any exploit available.

Detailsinfo

A vulnerability classified as problematic has been found in Joomla CMS up to 5.4.3/6.0.3. Affected is some unknown functionality of the component Multilingual Associations. The manipulation with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as CWE-79. 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. This is going to have an impact on integrity. CVE summarizes:

Lack of output escaping leads to a XSS vector in the multilingual associations component.

The weakness was released by Shirsendu Mondal, Md Tanzimul Alam Fahim and Unc Pembroke. The advisory is shared for download at developer.joomla.org. This vulnerability is traded as CVE-2026-21631 since 01/01/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation needs additional levels of successful authentication. Successful exploitation requires user interaction by the victim. There are neither technical details nor an exploit publicly available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 04/01/2026). The MITRE ATT&CK project declares the attack technique as T1059.007.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

Content Management System

Vendor

Joomla

Name

Version

License

open-source

Website

Vendor: https://www.joomla.org/

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA CVSS-B Score: 🔒
CNA CVSS-BT Score: 🔒
CNA Vector: 🔒

CVSSv3info

VulDB Meta Base Score: 2.4
VulDB Meta Temp Score: 2.4

VulDB Base Score: 2.4
VulDB Temp Score: 2.4
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AV	AC	Au	C	I	A
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💳	💳	💳	💳	💳	💳
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Vector	Complexity	Authentication	Confidentiality	Integrity	Availability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Cross site scripting
CWE: CWE-79 / CWE-94 / CWE-74
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

0-Day	Unlock	Unlock	Unlock	Unlock
Today	Unlock	Unlock	Unlock	Unlock

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: no mitigation known
Status: 🔍

0-Day Time: 🔒

Timelineinfo

01/01/2026 CVE reserved
04/01/2026 +89 days Advisory disclosed
04/01/2026 +0 days VulDB entry created
04/01/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: joomla.org

Advisory: developer.joomla.org
Researcher: Shirsendu Mondal, Md Tanzimul Alam Fahim, Unc Pembroke
Status: Confirmed

CVE: CVE-2026-21631 (🔒)
GCVE (CVE): GCVE-0-2026-21631
GCVE (VulDB): GCVE-100-354636

Entryinfo

Created: 04/01/2026 13:49
Changes: 04/01/2026 13:49 (68)
Complete: 🔍
Cache ID: 216::103