Discourse
CVE-2026-33393
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V8 - Authorization Access control enforcement
MITRE ATT&CK
1 technique across 1 tactic: Defense Evasion The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS 4.3. EPSS 0.0%. No patch confirmed. |
| Exploit ScenarioDerived | An attacker could exploit this vulnerability in Discourse to compromise the security of affected deployments, potentially impacting confidentiality, integrity, or availability. |
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Alert meAnalysisAIv1 – Mar 19, 2026
A remote code execution vulnerability in Discourse (CVSS 4.3). Remediation should follow standard vulnerability management procedures.
Earlier versions of this analysis (1)
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the allowed_spam_host_domains check used String#end_with? without domain boundary vali
RemediationAI
Monitor vendor channels for patch availability.
Affects your stack
Find out whether the stacks and servers you run are on an affected version.
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
CWE-284 (Improper Access Control). Affects Discourse.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
DescriptionGitHub Advisory
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the allowed_spam_host_domains check used String#end_with? without domain boundary validation, allowing domains like attacker-example.com to bypass spam protection when example.com was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by .) to prevent suffix-based bypass of newuser_spam_host_threshold. No known workarounds are available.
Executive ViewAI
Organizations using Discourse should be aware of moderate risk from CVE-2026-33393, a improper access control vulnerability rated CVSS 4.3. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)GitHub Advisory
Discourse versions prior to 3.5.0.beta6 contain a reflected cross-site scripting (XSS) vulnerability in social login fun
discourse-bbcode is the official BBCode plugin for Discourse. Rated critical severity (CVSS 9.8), this vulnerability is
Unauthorized information disclosure in Discourse discussion platform versions prior to 2026.3.0-latest.1, 2026.2.1, and
Discourse is an open source platform for community discussion. Rated high severity (CVSS 8.2), this vulnerability is rem
Discourse versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 contain an insecure direct object reference (IDOR) in the
In Discourse 2.7.0 through beta1, a rate-limit bypass leads to a bypass of the 2FA requirement for certain forms. Rated
Unauthenticated attackers can submit forged webhook payloads to multiple email provider integrations in Discourse versio
Discourse is an open-source discussion platform. Rated medium severity (CVSS 6.5), this vulnerability is remotely exploi
Discourse is an open source platform for community discussion. Rated medium severity (CVSS 5.9), this vulnerability is r
Discourse versions prior to 3.4.4 (stable), 3.5.0.beta5 (beta), and 3.5.0.beta6-dev (tests-passed) contain a critical vu
Discourse is an open source platform for community discussion. Rated critical severity (CVSS 9.8), this vulnerability is
Discourse Patreon enables syncronization between Discourse Groups and Patreon rewards. Rated critical severity (CVSS 9.8
Exploit-DB