Discourse
CVE-2026-26077
MEDIUM
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
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Lifecycle Timeline
2DescriptionGitHub 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.
AnalysisAI
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. …
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Vulnerability AssessmentAI
| Risk Assessment | CVSS 6.5 (MEDIUM). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker without authentication could exploit this vulnerability to compromise the affected system. |
| Remediation | Monitor vendor advisories for a patch. … Detailed patch versions, workarounds, and compensating controls in full report. |
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