CVE-2026-3254 | THREATINT

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.

PUBLISHED Reserved 2026-02-26 | Published 2026-04-22 | Updated 2026-04-22 | Assigner GitLab

LOW: 3.5CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N

Problem types

CWE-1021: Improper Restriction of Rendered UI Layers or Frames

Product status

Default status

unaffected

18.11 (semver) before 18.11.1

affected

Credits

Thanks [joaxcar](https://hackerone.com/joaxcar) for reporting this vulnerability through our HackerOne bug bounty program finder

References

hackerone.com/reports/3572752 (HackerOne Bug Bounty Report #3572752) technical-description exploit permissions-required

gitlab.com/gitlab-org/gitlab/-/work_items/591587

cve.org (CVE-2026-3254)

nvd.nist.gov (CVE-2026-3254)

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