Discourse: Onebox Domain Blocklist Bypass via Case-Sensitive Comparison

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-72721
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-10 16:19:49 UTC
Updated2026-08-10 17:17:36 UTC
DescriptionDiscourse 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

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

Problem Types: CWE-178 | CWE-178 CWE-178: Improper Handling of Case Sensitivity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Discourse Discourse affected < 2026.1.6 Not specified
CNA Discourse Discourse affected >= 2026.5.0-latest, < 2026.5.2 Not specified
CNA Discourse Discourse affected >= 2026.6.0-latest, < 2026.6.1 Not specified
CNA Discourse Discourse affected >= 2026.7.0-latest, < 2026.7.0 Not specified

References

ReferenceSourceLinkTags
github.com/discourse/discourse/security/advisories/GHSA-3x7x-24rq-h5j6 [email protected] github.com
github.com/discourse/discourse/commit/f503971d311b7b0dfdb751ee8cfd67e8cb... [email protected] github.com
github.com/discourse/discourse/commit/c2eb6b0e5597d6f28f4be739b83300bc9c... [email protected] github.com
github.com/discourse/discourse/commit/caa615c371b1696982ee11ac8f3558f0f8... [email protected] github.com
github.com/discourse/discourse/pull/42093 [email protected] github.com
github.com/discourse/discourse/pull/42092 [email protected] github.com
github.com/discourse/discourse/commit/a3e10759fef47f03d450649bb51d9e84f4... [email protected] github.com
github.com/discourse/discourse/pull/42091 [email protected] github.com
github.com/discourse/discourse/pull/42094 [email protected] github.com
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