CVE-2026-91123
Discourse: Reject literal backslash path separators in iframe src traversal guard
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
Description
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.
Timeline
ID reserved
By GitHub_M
- 10 days later
· 10 days later
Published
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 3.1 | High7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| NVDNVD · Deferred | 3.1 | High7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
- EPSS (exploitation in 30 days)
- 0.29% · top 79% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: yes · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.2.
Weakness
Affected products
References (6)
- https://github.com/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc (opens in a new tab)x_refsource_CONFIRM
- https://github.com/discourse/discourse/pull/42882 (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318 (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24 (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be (opens in a new tab)x_refsource_MISC
- https://github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-91123)Record last updated .