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TI-2026-38928 Aliases CVE-2026-53961

Discourse: Forged AWS SNS bounce notifications can disable a targeted user's email (missing TopicArn binding)

Priority LOW 35CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
None · Low · Low
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-345.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.003 22nd percentileScored 2026-11-07
Fix Fixed discourse (discourse): 2026.5.1, 2026.4.2, 2026.1.5

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
discoursediscourse2026.5.0-latest to before 2026.5.1; 2026.4.0-latest to before 2026.4.2; 2026.1.0-latest to before 2026.1.52026.5.1, 2026.4.2, 2026.1.5Patch availableCNA
  • discourse Vendordiscourse Affected 2026.5.0-latest to before 2026.5.1; 2026.4.0-latest to before 2026.4.2; 2026.1.0-latest to before 2026.1.5 Fixed in 2026.5.1, 2026.4.2, 2026.1.5 Patch available CNA

CPE configurations NVD · 2

CPEVersionsRoleVendor
cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:*2026.1.0 to before 2026.1.5; 2026.4.0 to before 2026.4.2; 2026.5.0 to before 2026.5.1Vulnerablediscourse
cpe:2.3:a:discourse:discourse:2026.6.0:*:*:*:latest:*:*:*2026.6.0Vulnerablediscourse
  • cpe:2.3:a:discourse:discourse:*:*:*:*:*:*:*:* Versions 2026.1.0 to before 2026.1.5; 2026.4.0 to before 2026.4.2; 2026.5.0 to before 2026.5.1 Vulnerable ·discourse
  • cpe:2.3:a:discourse:discourse:2026.6.0:*:*:*:latest:*:*:* Versions 2026.6.0 Vulnerable ·discourse

Remediation

  • Fix · CNA discourse (discourse) Fixed in 2026.5.1, 2026.4.2, 2026.1.5

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-53961

References

Patch 4

Advisory 1

Other 4

  • TI-2021-19656 Denial of Service in discourse CVSS 3.1MEDIUM 6.8
  • TI-2024-36150 Potential Backup file leaked via Nginx in Discourse CVSS 3.1HIGH 7.5
  • TI-2021-18002 RCE via malicious SNS subscription payload CVSS 3.1CRITICAL 10.0
  • TI-2026-24651 Discourse: Open redirect via `sso_destination_url` cookie in `enter` CVSS 4.0MEDIUM 5.1
  • TI-2026-22278 Discourse leaks private topic title and post excerpt via user action API endpoint CVSS 4.0HIGH 8.7
  • TI-2023-24152 Unauthenticated access to new private chat messages in Discourse CVSS 3.1HIGH 7.5
See all 262 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences