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Discourse EUVDEUVD-2026-42730

| CVE-2026-49256 MEDIUM
Information Exposure (CWE-200)
2026-07-09 security-advisories@github.com
Information Disclosure Discourse
6.3
CVSS 4.0 · Vendor: github
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Severity by source

Vendor (github) PRIMARY
6.3 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vuln.today AI
3.7 LOW

AC:H maps the CVSS 4.0 AT:P precondition; PR:N because no auth needed once conditions exist; C:L for tag-name-only disclosure with no integrity or availability impact.

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

Primary rating from Vendor (github).

CVSS VectorVendor: github

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

2
Patch available
Jul 09, 2026 - 23:02 EUVD
Analysis Generated
Jul 09, 2026 - 22:43 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, restricted tag and tag-group names attached to publicly readable categories as allowed_tags, allowed_tag_groups, or required tag groups could leak to anonymous and unauthorized users through category and group endpoints. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

AnalysisAI

Restricted tag and tag-group name disclosure in Discourse exposes internal taxonomy metadata to anonymous and unauthorized users via the category and group API endpoints. All Discourse versions prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5 are affected when restricted tags or tag groups are configured on publicly readable categories. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Identify public Discourse instance
Delivery
Query /categories.json or group endpoint unauthenticated
Exploit
Parse JSON response for tag and tag-group fields
Execution
Extract restricted tag and tag-group names
Impact
Record organizational metadata for reconnaissance
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Vulnerability AssessmentAI

Exploitation Exploitation requires that the target Discourse instance has at least one restricted tag or restricted tag group assigned as allowed_tags, allowed_tag_groups, or a required tag group on a publicly readable category. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 4.0 score of 6.3 (Medium) accurately reflects the limited blast radius: AV:N/AC:L/PR:N/UI:N indicate the endpoint is trivially reachable by any unauthenticated actor, but AT:P confirms that exploitation is gated on a specific administrator-configured precondition (restricted tags attached to public categories). … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An unauthenticated attacker sends a standard HTTP GET request to a public Discourse forum's /categories.json or equivalent group endpoint. The JSON response includes the names of restricted tags and tag groups attached to publicly readable categories, which the attacker records for organizational intelligence gathering or targeted social engineering. …
Remediation Upgrade Discourse to one of the patched releases: v2026.6.0, v2026.5.1, v2026.4.2, or v2026.1.5, as documented in the GitHub Security Advisory at https://github.com/discourse/discourse/security/advisories/GHSA-mwp7-572g-6qpx. … Detailed patch versions, workarounds, and compensating controls in full report.
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EUVD-2026-42730 vulnerability details – vuln.today
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