CVE-2026-72721

MEDIUM 5.3

Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison

CVSS Score

5.3

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-178
Vendor	discourse
Product	discourse
Published	Aug 10, 2026
Last Updated	Aug 10, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Affected Versions

discourse / discourse

< 2026.1.6 >= 2026.5.0-latest, < 2026.5.2 >= 2026.6.0-latest, < 2026.6.1 >= 2026.7.0-latest, < 2026.7.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗