CVE-2026-91123

Discourse: Reject literal backslash path separators in iframe src traversal guard

Published: Sep 24, 2026Updated: Sep 24, 2026 Sources: CVE List NVDCWE-22

7.2HIGH

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.

No summary for this CVE yet.

CVSS Vector Breakdown

Exploitability

AV:NAttack Vector

Network

AC:LAttack Complexity

Low

PR:NPrivileges Required

None

UI:NUser Interaction

None

Scope

S:CScope

Changed

Impact

C:LConfidentiality

Low

I:LIntegrity

Low

A:NAvailability

None

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Weaknesses

CWE-22

Affected Products

discourse

commercial·USaka discourse.org

discourse

Web & CMS Plugins

Exploitability

No known exploits, KEV entries, or remediation guidance available for this vulnerability yet.

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Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

2 techniques

Collection

Discovery

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References

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

and 3 more references View all →

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