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

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Summary

CVECVE-2026-53961
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-09 22:17:05 UTC
Updated2026-07-10 15:53:08 UTC
DescriptionDiscourse 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.

Risk And Classification

Primary CVSS: v3.1 6.5 MEDIUM from [email protected]

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

Problem Types: CWE-345 | CWE-345 CWE-345: Insufficient Verification of Data Authenticity

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
3.1CNADECLARED6.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

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

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Discourse Discourse affected >= 2026.5.0-latest, < 2026.5.1 Not specified
CNA Discourse Discourse affected >= 2026.4.0-latest, < 2026.4.2 Not specified
CNA Discourse Discourse affected >= 2026.1.0-latest, < 2026.1.5 Not specified

References

ReferenceSourceLinkTags
github.com/discourse/discourse/commit/3a3d315a85ef3c6aabfc7e7bb387020597... [email protected] github.com
github.com/discourse/discourse/commit/958f0cd831d65a49ec75f05343ca2c1676... [email protected] github.com
github.com/discourse/discourse/releases/tag/v2026.5.1 [email protected] github.com
github.com/discourse/discourse/releases/tag/v2026.6.0 [email protected] github.com
github.com/discourse/discourse/releases/tag/v2026.1.5 [email protected] github.com
github.com/discourse/discourse/commit/61f12e13aa1b760f81d5ff60f12e3a7e77... [email protected] github.com
github.com/discourse/discourse/commit/aea35190791261bab258ebab05da279e78... [email protected] github.com
github.com/discourse/discourse/releases/tag/v2026.4.2 [email protected] github.com
github.com/discourse/discourse/security/advisories/GHSA-8f9m-v436-wr3x [email protected] github.com
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