Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, the enter action in StaticController reads the sso_destination_url cookie and redirects to it with allow_other_host: true without validating the destination URL. While this cookie is normally set during legitimate DiscourseConnect Provider flows with cryptographically validated SSO payloads, cookies are client-controlled and can be set by attackers.
This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
High
Difficult to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
Active
User action required
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products 4
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:*:*:*:*:latest:*:*:*
|
2026.1.0
|
2026.1.3
|
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:*:*:*:*:latest:*:*:*
|
2026.2.0
|
2026.2.2
|
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*
|
— | — |
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest.1:*:*:*
|
— | — |
References 4
https://github.com/discourse/discourse/commit/080408b93d00305b51d71f63f755f43fa…
security-advisories@github.com
https://github.com/discourse/discourse/security/advisories/GHSA-378j-ccw4-4fwh
security-advisories@github.com
https://meta.discourse.org/t/using-discourse-as-a-sso-provider/32974
security-advisories@github.com
https://meta.discourse.org/t/use-discourse-as-an-identity-provider-sso-discours…
134c704f-9b21-4f2e-91b3-4a467353bcc0