CVE-2026-72721
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…
Does this matter?
Lower severity and a low EPSS score (0.43%). Track it; it rarely justifies an emergency change on its own.
Description
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.
- CVSS 3.1
- 5.3 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- EPSS
- 0.43% probability · 36th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-178
- Source
- security-advisories@github.com
References
- https://github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4c68b8f
- https://github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c69e3cd
- https://github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8ced584
- https://github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb99f5c5
- https://github.com/discourse/discourse/pull/42091
- https://github.com/discourse/discourse/pull/42092
- https://github.com/discourse/discourse/pull/42093
- https://github.com/discourse/discourse/pull/42094
- https://github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.