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Discourse CVE-2026-45775

| EUVD-2026-36559 MEDIUM
Path Traversal (CWE-22)
2026-06-12 GitHub_M
Path Traversal Discourse
6.8
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

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

PR:H confirmed by admin-only access requirement; S:C reflects cross-site trust boundary violation; I:N and A:N as no write or availability impact exists.

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

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

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

Lifecycle Timeline

2
Patch available
Jun 12, 2026 - 22:01 EUVD
Analysis Generated
Jun 12, 2026 - 21:31 vuln.today

DescriptionCVE.org

Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.4, 2026.3.0-latest to before 2026.3.1, and 2026.4.0-latest to before 2026.4.1, a path traversal vulnerability in Discourse backup handling could allow an authenticated administrator on one site in a multisite deployment to access backup files belonging to another site when backups are stored locally. In affected configurations, an admin on Site A could potentially retrieve sensitive backup data from Site B (same host, multisite) by crafting a backup download request with a traversal payload. This issue has been patched in versions 2026.1.4, 2026.3.1, 2026.4.1, and 2026.5.0-latest.1.

AnalysisAI

Path traversal in Discourse's backup download handler allows an authenticated administrator on one site within a multisite deployment to retrieve backup archives belonging to a co-hosted site on the same server. Backup files typically contain full database dumps, private messages, user credentials, and email addresses, making cross-site access a serious trust-boundary violation. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Obtain or compromise admin account on Site A
Delivery
Identify target site's backup directory or filename
Exploit
Craft HTTP backup download request with path traversal payload
Execution
Submit authenticated request to Discourse backup endpoint
Persist
Server resolves traversal to Site B backup path
Impact
Exfiltrate Site B backup archive containing full database dump
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Vulnerability AssessmentAI

Exploitation Exploitation requires three concurrent structural conditions: (1) the attacker must hold an active, valid administrator account on at least one site within the Discourse deployment - this is a high-privilege requirement confirmed by CVSS PR:H; (2) Discourse must be running in multisite mode, where two or more sites share a single application host and filesystem; and (3) Discourse must be configured to store backups locally on the server filesystem, not in a remote object store such as S3. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 score of 6.8 is driven upward by the scope change (S:C) and high confidentiality impact (C:H), reflecting that exploitation crosses a site-isolation boundary to expose another system's sensitive data. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker who has legitimately or illicitly obtained administrator credentials for Site A in a Discourse multisite deployment submits a crafted backup download request to the Discourse backup endpoint, embedding path traversal sequences such as '../../site_b_backup_dir/latest.tar.gz' in the filename parameter. The unpatched server resolves the traversal without restriction and streams Site B's backup archive - containing its full database dump, user accounts, private messages, and hashed or plaintext credentials - back to the attacker. …
Remediation Upgrade Discourse to version 2026.1.4 (2026.1.x release train), 2026.3.1 (2026.3.x train), 2026.4.1 (2026.4.x train), or 2026.5.0-latest.1 (latest track) as confirmed by the vendor advisory at https://github.com/discourse/discourse/security/advisories/GHSA-5j6v-4x6g-9pg5. … Detailed patch versions, workarounds, and compensating controls in full report.
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CVE-2026-45775 vulnerability details – vuln.today
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