Path Traversal in Discourse
CVE-2026-91123
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.
Vulnerability class: Path Traversal (Directory Traversal)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Discourse — versions < 2026.8.0, >= 2026.1.0-latest, < 2026.1.8, >= 2026.6.0-latest, < 2026.6.3
Weakness classification (CWE)
References
- github.com/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc
- github.com/discourse/discourse/pull/42882
- github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318
- github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24
- github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be
- github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579
Frequently asked questions
- What is CVE-2026-91123?
- CVE-2026-91123 is a high-severity vulnerability in Discourse, classified under Path Traversal. CVSS score: 7.2/10. Published 2026-09-24.
- How severe is CVE-2026-91123?
- High severity. CVSS v3 base score is 7.2 out of 10.