Discourse
CVE-2026-26077
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A07:2025 - Authentication Failures
ASVS 5.0
V6 - Authentication Authentication mechanism validation
MITRE ATT&CK
2 techniques across 2 tactics: Defense Evasion, Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS 6.5 (MEDIUM). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. Exploitation no authentication required. |
| Exploit ScenarioDerived | An attacker without authentication could exploit this vulnerability to compromise the affected system. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Unauthenticated attackers can submit forged webhook payloads to multiple email provider integrations in Discourse versions prior to 2025.12.2, 2026.1.1, and 2026.2.0 when authentication tokens are not configured, allowing them to artificially inflate user bounce scores and disable legitimate user accounts. The vulnerability affects webhook endpoints for SendGrid, Mailjet, Mandrill, Postmark, and SparkPost, with Mailpace having no token validation whatsoever. Administrators should immediately configure webhook authentication tokens for all email provider integrations as a workaround until patching is available.
Earlier versions of this analysis (1)
Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, several webhook endpoints (SendGrid, Mailjet, Mandrill, Postmark, SparkPost) in the WebhooksController accepted requests without a valid authentication token when no token was configured. [CVSS 6.5 MEDIUM]
RemediationAI
Monitor vendor advisories for a patch. Restrict network access to the affected service where possible.
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
Classified as CWE-287 (Improper Authentication). Affects Discourse. Discourse is an open source discussion platform. Prior to versions 2025.12.2, 2026.1.1, and 2026.2.0, several webhook endpoints (SendGrid, Mailjet, Mandrill, Postmark, SparkPost) in the WebhooksController accepted requests without a valid authentication token when no token was configured. This allowed unauthenticated attackers to forge webhook payloads and artificially inflate user bounce scores, potentially causing legitimate user emails to be disabled. The Mailpace endpoint had no token vali
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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:N/UI:N/S:U/C:N/I:L/A:L
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 2025.12.2, 2026.1.1, and 2026.2.0, several webhook endpoints (SendGrid, Mailjet, Mandrill, Postmark, SparkPost) in the WebhooksController accepted requests without a valid authentication token when no token was configured. This allowed unauthenticated attackers to forge webhook payloads and artificially inflate user bounce scores, potentially causing legitimate user emails to be disabled. The Mailpace endpoint had no token validation at all. Starting in versions 2025.12.2, 2026.1.1, and 2026.2.0, all webhook endpoints reject requests with a 406 response when no authentication token is configured. As a workaround, ensure that webhook authentication tokens are configured for all email provider integrations in site settings (e.g., sendgrid_verification_key, mailjet_webhook_token, postmark_webhook_token, sparkpost_webhook_token). There's no current workaround for mailpace before getting this fix.
Executive ViewAI
Organizations using Discourse should be aware of notable risk from CVE-2026-26077, a improper authentication vulnerability rated CVSS 6.5. This could allow unauthorized access to protected resources. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: restrict network access, enable MFA, monitor auth logs.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
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
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