CVE-2026-72721

Summary

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, Onebox::DomainChecker.is_blocked? compares hostnames and SiteSetting.blocked_onebox_domains entries case-sensitively, allowing an attacker to bypass configured Onebox domain restrictions by changing character casing in a redirect target hostname. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

Affected Software

VendorProductVersion RangeStatus
discoursediscourse< 2026.1.6affected
discoursediscourse>= 2026.5.0-latest, < 2026.5.2affected
discoursediscourse>= 2026.6.0-latest, < 2026.6.1affected
discoursediscourse>= 2026.7.0-latest, < 2026.7.0affected

Weaknesses

  • CWE-178: CWE-178: Improper Handling of Case Sensitivity

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: yes
    • Technical Impact: partial

References