CVE-2026-91123
Discourse: Reject literal backslash path separators in iframe src traversal guard
CVSS Score
7.2
EPSS Score
0.0%
EPSS Percentile
0th
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
| CWE | CWE-22 |
| Vendor | discourse |
| Product | discourse |
| Published | Sep 24, 2026 |
| Last Updated | Sep 24, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None
Affected Versions
discourse / discourse
< 2026.8.0 >= 2026.7.0-latest, < 2026.7.2 >= 2026.6.0-latest, < 2026.6.3 >= 2026.1.0-latest, < 2026.1.8
References
github.com: https://github.com/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc github.com: https://github.com/discourse/discourse/pull/42882 github.com: https://github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318 github.com: https://github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24 github.com: https://github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be github.com: https://github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579