CVE-2026-23891

CRITICAL

Decidim has a cross-site scripting (XSS) in user name

Published April 13, 2026Updated May 13, 2026Source: osv

Summary

### Impact A stored code execution vulnerability in the user name field allows a low-privileged attacker to execute arbitrary code in the context of any user who passively visits a comment page, resulting in high confidentiality and integrity impact across security boundaries. ### Patches N/A ### Workarounds Not available ### References OWASP ASVS v4.0.3-5.1.3 ### Credits This issue was discovered in a security audit organized by [octree](https://octree.ch/) and made by [Secu Labs](https://seculabs.ch/) against Decidim financed by the city of Lausanne (Switzerland).

Remediation

Upgrade to the fixed version using your package manager.

Bundler

Update decidim-core to 0.30.5 or later

gem install decidim-core -v 0.30.5

Bundler

Update decidim-core to 0.31.1 or later

gem install decidim-core -v 0.31.1

After upgrading, run your dependency scanner again to confirm the vulnerability is resolved.

Affected Packages (2)

Package	Ecosystem	Affected	Fixed In
decidim-core	rubygems	0.0.1, 0.0.1.alpha1, 0.0.1.alpha2, 0.0.1.alpha3 (+154 more)	0.30.5
decidim-core	rubygems	0.31.0, 0.31.0.rc1, 0.31.0.rc2	0.31.1

Vulnerability Classification

Common Weakness Enumeration (CWE) identifiers for this vulnerability type.

CWE-79
Cross-site Scripting (XSS)MITRE

CVSS Score Breakdown

What the CVSS (Common Vulnerability Scoring System) 8.7 score means for each attack dimension.

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

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

References

Frequently Asked Questions

What is CVE-2026-23891?: Decidim has a cross-site scripting (XSS) in user name This vulnerability has been assigned a severity rating of CRITICAL (CVSS score: 8.7/10).
How do I check if my project is affected by CVE-2026-23891?: CVE-2026-23891 affects decidim-core. Use GeekWala's free vulnerability scanner to check your dependencies against CVE-2026-23891 and 200,000+ other known vulnerabilities.

Severity & Exploitability

CVSS Score

8.7

High exploitability or significant impact. Prioritize remediation within days.

Also Known As

GHSA-fc46-r95f-hq7g

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