BIT-discourse-2026-53961: Discourse: Forged AWS SNS bounce notifications can disable a targeted user's email (missing TopicArn binding)
Discourse versions prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5 contain a vulnerability in the AWS SES bounce webhook. The webhook verified that SNS messages were signed by Amazon but failed to restrict them to trusted TopicArn values. This allowed any AWS account holder to send validly signed forged bounce notifications, which could disable a targeted user's email. The issue is fixed in the specified patched versions.
AI Analysis
Technical Summary
Discourse's AWS SES bounce webhook endpoint at POST /webhooks/aws verified the authenticity of SNS messages by checking their Amazon signature but did not bind these messages to specific trusted TopicArn values. This lack of TopicArn binding allowed attackers with any AWS account to publish forged bounce notifications that appeared valid, enabling them to revoke or disable targeted user emails. The vulnerability affects Discourse versions before 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5 and has been addressed in these versions.
Potential Impact
An attacker with any AWS account can send forged bounce notifications to the Discourse AWS SES bounce webhook, causing the targeted user's email to be disabled. This could disrupt user communications and potentially impact user account recovery or notifications reliant on email.
Mitigation Recommendations
Upgrade Discourse to version 2026.6.0, 2026.5.1, 2026.4.2, or 2026.1.5 or later, where the issue is fixed by binding SNS messages to trusted TopicArn values. Applying these official fixes will prevent acceptance of forged bounce notifications.
BIT-discourse-2026-53961: Discourse: Forged AWS SNS bounce notifications can disable a targeted user's email (missing TopicArn binding)
Description
Discourse versions prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5 contain a vulnerability in the AWS SES bounce webhook. The webhook verified that SNS messages were signed by Amazon but failed to restrict them to trusted TopicArn values. This allowed any AWS account holder to send validly signed forged bounce notifications, which could disable a targeted user's email. The issue is fixed in the specified patched versions.
Affected software
pkg:bitnami/discourseRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Discourse's AWS SES bounce webhook endpoint at POST /webhooks/aws verified the authenticity of SNS messages by checking their Amazon signature but did not bind these messages to specific trusted TopicArn values. This lack of TopicArn binding allowed attackers with any AWS account to publish forged bounce notifications that appeared valid, enabling them to revoke or disable targeted user emails. The vulnerability affects Discourse versions before 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5 and has been addressed in these versions.
Potential Impact
An attacker with any AWS account can send forged bounce notifications to the Discourse AWS SES bounce webhook, causing the targeted user's email to be disabled. This could disrupt user communications and potentially impact user account recovery or notifications reliant on email.
Mitigation Recommendations
Upgrade Discourse to version 2026.6.0, 2026.5.1, 2026.4.2, or 2026.1.5 or later, where the issue is fixed by binding SNS messages to trusted TopicArn values. Applying these official fixes will prevent acceptance of forged bounce notifications.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- BIT-discourse-2026-53961
- Osv Schema Version
- 1.6.2
- Aliases
- ["CVE-2026-53961"]
- Ecosystems
- ["Bitnami"]
- Database Specific Severity
- Medium
- Cvss Version
- null
Threat ID: 6a58b51a68715ace43db4595
Added to database: 07/16/2026, 10:40:26 UTC
Last enriched: 07/16/2026, 14:29:43 UTC
Last updated: 07/17/2026, 02:25:29 UTC
Views: 13
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