CVE-2026-91123 json
Discourse: Reject literal backslash path separators in iframe src traversal guard
published 2026-09-24 45 d ago modified 2026-10-01 39 d ago also BIT-discourse-2026-91123 , EUVD-2026-86300 , GHSA-6pwj-wgg8-4rjc
- cvss
- 7.2
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 21%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- bitnami discourse 2026.8.0
- discourse discourse 2026.1.8, 2026.6.3, 2026.7.2, 2026.8.0
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 45 d ago
Exploit prediction
0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
| OSV | 3.1 | 7.2 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| bitnami | discourse | <2026.8.0 |
2026.8.0 |
Affected products
- discourse discourse
Classification
- Weakness
-
- CWE-22 Improper Limitation of a Pathname to a Restricted Directory
References
-
github.com
/discourse/discourse/pull/42882
web
-
github.com
/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318
web
-
github.com
/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24
web
-
github.com
/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be
web
-
github.com
/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579
web
-
github.com
/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-91123
web
Sources
- CVE List CVE-2026-91123
- NVD CVE-2026-91123
- OSV BIT-discourse-2026-91123
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.