What is the CVSS score of CVE-2026-27740?

CVE-2026-27740 has a CVSS 3.1 base score of 6.1 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N. EPSS exploitation probability: 0.0%.

Which versions of Discourse are affected by CVE-2026-27740?

Organizations using Discourse should be aware of moderate risk from CVE-2026-27740, a cross-site scripting vulnerability rated CVSS 6.1.. A patch is available.

How to fix or mitigate CVE-2026-27740?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Verify Content-Security-Policy and output encoding.

Discourse CVE-2026-27740

EUVD-2026-13194 MEDIUM

Cross-site Scripting (XSS) (CWE-79)

2026-03-19 security-advisories@github.com

XSS Discourse

6.1

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

6.1 MEDIUM

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

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Lifecycle Timeline

Patch available

Apr 16, 2026 - 05:29 EUVD

2026.1.2,2026.2.1

EUVD ID Assigned

Mar 19, 2026 - 21:30 euvd

EUVD-2026-13194

Analysis Generated

Mar 19, 2026 - 21:30 vuln.today

CVE Published

Mar 19, 2026 - 21:17 nvd

MEDIUM 6.1

DescriptionGitHub Advisory

Discourse is an open-source discussion platform. Versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 have a cross-site scripting vulnerability that arises because the system trusts the raw output from an AI Large Language Model (LLM) and renders it using htmlSafe in the Review Queue interface without adequate sanitization. A malicious attacker can use valid Prompt Injection techniques to force the AI to return a malicious payload (e.g., tags). When a Staff member (Admin/Moderator) views the flagged post in the Review Queue, the payload executes. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, temporarily disable AI triage automation scripts.

AnalysisAI

Cross-site scripting in Discourse's Review Queue interface allows remote attackers to inject malicious payloads through prompt injection attacks against the AI triage system, which renders unsanitized LLM output to staff members. When administrators or moderators view flagged posts, the injected payload executes in their browser context, potentially compromising their sessions or performing unauthorized actions. The vulnerability affects Discourse versions prior to 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, with patches available in these releases.