CVE-2026-53961: Discourse

Medium severity, CVSS 6.5. EPSS: 0.3% chance of exploitation in the next 30 days.

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, the AWS SES bounce webhook at POST /webhooks/aws verified that SNS messages were signed by Amazon but did not bind them to trusted TopicArn values, allowing any AWS account holder to publish validly signed forged Bounce notifications that revoke a targeted user email. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

Affected products

• Discourse Discourse: from 2026.1.0, before 2026.1.5 (fixed in 2026.1.5); from 2026.4.0, before 2026.4.2 (fixed in 2026.4.2); from 2026.5.0, before 2026.5.1 (fixed in 2026.5.1); version 2026.6.0 only

Published 2026-07-09. Last modified 2026-07-14.