CVE-2026-26077
Discourse doesn't ensure webhooks require a token
Description
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.
How to fix CVE-2026-26077
To remediate CVE-2026-26077, upgrade the affected package to a fixed version below.
- —upgrade to 2025.12.2 or later
Is CVE-2026-26077 being exploited?
Low — EPSS is 0.2%, meaning exploitation activity has not been observed at scale.
Affected packages (1)
- from 0, < 2025.12.2, >= 2026.1.0, < 2026.1.1
CVSS scores
| Source | Version | Severity | Vector |
|---|---|---|---|
| osv | CVSS 3.1 | MEDIUM6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |