CVE-2026-27740

5.1 MEDIUM 0.3% exploit odds Fix listed XSS

What it is

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.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account, but needs a user to act. Limited direct impact.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-03-19 21:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 10:27 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.3% in the next 30 days (EPSS).
Severity: 5.1 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-03-19 21:17 UTC
Last modified: 2026-06-17 10:27 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-79 · Cross-site scripting
Record status: Analyzed

Affected

Discourse < 2026.1.2
Discourse < 2026.2.1
Discourse 2026.3.0

Attack profile CVSS 4.0 · 5.1

Attack vector: Network
Complexity: Low
Attack requirements: None
Privileges needed: Low
User interaction: Passive
Confidentiality: Low
Integrity: Low
Availability: None

Raw vector

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-27740.md and follow it. Check whether this project is affected by CVE-2026-27740. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

· More options · Status badge

Download Square Reddit

Fix and advisories

References

NVD record · CVE.org record