How serious is CVE-2026-26077?

This vulnerability has a CVSS score of 6.5 out of 10, classified as MEDIUM severity. No public exploit code has been identified yet.

Which products are affected by CVE-2026-26077?

CVE-2026-26077 affects discourse discourse. Check the full CVE details for specific version information.

How do I fix CVE-2026-26077?

To remediate CVE-2026-26077, check for security patches from discourse. Apply all available updates and security patches. If no patch is available, implement recommended workarounds or security controls to mitigate the risk.

CVE-2026-26077

Medium

|6.5

No Exploit

Plain English Summary

AI-powered analysis for quick understanding

This vulnerability allows attackers to send fake data to certain email service integrations on the Discourse platform, which can lead to legitimate user emails being mistakenly marked as undeliverable. It occurs when no authentication token is set up, meaning attackers can exploit this weakness without needing any special access.

Technical 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.

CVSS Vector Analysis

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

Confidentiality ImpactNone

Integrity ImpactLow

Availability ImpactLow

ScopeUnchanged

Vector String

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Exploit Resources

Search for proof-of-concept code and exploit modules

GitHub Search Exploit-DB Nuclei Templates Metasploit Vulners

Official References

NIST NVD

Est. Bounty

$931($500-$1K)

Vendor Response

Grade APatched in 4 days

Quick Information

Published

Feb 26, 2026

about 1 month ago

Last Modified

Mar 2, 2026

about 1 month ago

Vendor

discourse

Product

discourse

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