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Discourse CVE-2026-46413

| EUVDEUVD-2026-42729 MEDIUM
Missing Authorization (CWE-862)
2026-07-09 security-advisories@github.com
Authentication Bypass Discourse
6.5
CVSS 3.1 · Vendor: github
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Severity by source

Vendor (github) PRIMARY
6.5 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
vuln.today AI
6.5 MEDIUM

Network-exploitable web app requiring only a low-privilege account; write-only impact to admin storage with no confidentiality or availability consequence.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (github).

CVSS VectorVendor: github

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

Lifecycle Timeline

2
Patch available
Jul 09, 2026 - 23:02 EUVD
Analysis Generated
Jul 09, 2026 - 22:42 vuln.today

DescriptionCVE.org

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, regular users could route direct S3 multipart uploads through ExternalUploadManager into the admin backup store. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

AnalysisAI

Unauthorized write access to the admin backup store in Discourse allows any authenticated regular user to route S3 multipart uploads into a storage area that should be restricted to administrators. The flaw exists in ExternalUploadManager, which fails to enforce authorization checks (CWE-862) when accepting direct S3 multipart upload requests, meaning a low-privilege account holder can target the admin backup destination path without restriction. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Authenticate as regular Discourse user
Delivery
Initiate S3 multipart upload via ExternalUploadManager API
Exploit
Manipulate destination parameter to target admin backup store prefix
Execution
Server skips authorization check (CWE-862)
Impact
Attacker-controlled file written to admin backup store
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Vulnerability AssessmentAI

Exploitation Exploitation requires the attacker to hold a valid regular user account on the target Discourse instance (PR:L per CVSS vector). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 score of 6.5 (Medium) with vector AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N accurately reflects the threat profile: network-exploitable over standard HTTP, low attack complexity, requiring only a regular user account (PR:L), with no user interaction needed. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker registers or already holds a standard (non-admin) account on a Discourse instance configured with direct S3 multipart uploads. They initiate an upload via ExternalUploadManager, manipulating the upload destination parameter to target the admin backup store S3 prefix rather than the user content bucket. …
Remediation Vendor-released patches are confirmed at versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, available at github.com/discourse/discourse/releases. … Detailed patch versions, workarounds, and compensating controls in full report.
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Same weakness CWE-862 – Missing Authorization

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CVE-2026-46413 vulnerability details – vuln.today
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