CVE-2026-91123CWE-22path-traversal

CVE-2026-91123

High · published September 24, 2026

CVSS v3.1
7.2
EPSS
0%
Percentile
20.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.2 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00287 · 20.1th percentile
Weakness
CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Published
2026-09-24T21:17Z
References (6)
https://github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318 · [email protected]https://github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24 · [email protected]https://github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be · [email protected]https://github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579 · [email protected]https://github.com/discourse/discourse/pull/42882 · [email protected]https://github.com/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc · [email protected]
EPSS history
Timeline
  • 26 SEP 03:27Z
    EPSS moved — → 0%
    epss
  • 24 SEP 16:54Z
    Discourse: Reject literal backslash path separators in iframe src traversal guard
    cvelistv5