What is the CVSS score of CVE-2026-27166?

CVE-2026-27166 has a CVSS 3.1 base score of 4.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Discourse are affected by CVE-2026-27166?

Organizations using Discourse should be aware of moderate risk from CVE-2026-27166 rated CVSS 4.1. Exploitation could compromise the security of affected deployments.. A patch is available.

How to fix or mitigate CVE-2026-27166?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Discourse CVE-2026-27166

EUVD-2026-13187 MEDIUM

Basic XSS (CWE-80)

2026-03-19 GitHub_M

XSS Discourse

4.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

4.1 MEDIUM

AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

Required

Scope

Changed

Confidentiality

None

Integrity

Low

Availability

None

Lifecycle Timeline

Patch available

Apr 16, 2026 - 05:29 EUVD

2026.1.2,2026.3.0-latest.1,2026.2.1

EUVD ID Assigned

Mar 19, 2026 - 21:00 euvd

EUVD-2026-13187

Analysis Generated

Mar 19, 2026 - 21:00 vuln.today

CVE Published

Mar 19, 2026 - 20:29 nvd

MEDIUM 4.1

DescriptionGitHub Advisory

Discourse is an open source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2, insufficient cleanup in the default Codepen allowed iframes value allows an attacker to trick a user into changing the URL of the main page. This issue has been fixed in versions 2026.3.0-latest.1, 2026.2.1 and 2026.1.2. To workaround this issue, remove Codepen from the list of allowed iframes.

AnalysisAI

Insufficient sanitization of Codepen iframe parameters in Discourse prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 allows authenticated attackers to manipulate users into changing the main page URL through social engineering. The vulnerability requires user interaction and network access but has no available patch, making disabling Codepen embeds the recommended mitigation.

Technical ContextAI

Cross-site scripting (XSS) allows injection of client-side scripts into web pages viewed by other users due to insufficient output encoding. This vulnerability is classified as Basic XSS (CWE-80).