{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-86351", "assignerOrgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "state": "PUBLISHED", "assignerShortName": "CIRCL", "dateReserved": "2026-09-07T09:59:32.940Z", "datePublished": "2026-09-07T09:59:34.850Z", "dateUpdated": "2026-09-07T09:59:34.850Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "MISP", "repo": "https://github.com/MISP/MISP", "vendor": "MISP", "versions": [{"lessThanOrEqual": "2.5.45", "status": "affected", "version": "0", "versionType": "semver"}]}], "credits": [{"lang": "en", "type": "finder", "value": "Scottish Government - National Cyber Team"}, {"lang": "en", "type": "remediation developer", "value": "iglocska"}, {"lang": "en", "type": "remediation developer", "value": "Claude Opus 5 (1M context)"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Affected versions of MISP validate the user-configurable homepage by checking only whether the supplied path begins with <code>/</code>. That check is insufficient because protocol-relative URLs such as <code>//attacker.example</code> also begin with <code>/</code> but resolve to an external origin in browsers.</p>\n<p>The vulnerable homepage value can be stored as a user setting and later used by the post-login routing logic. The commit explicitly identifies <code>//attacker.example</code> as a payload that passed validation and was emitted to the <code>Location</code> header after login.</p><p>The fix introduces a shared <code>InternalRedirectValidator</code> that rejects URLs containing a host, scheme, userinfo, unsafe leading <code>//</code> or <code>/\\</code>, malformed URLs, and control characters. It also revalidates homepage settings on read so legacy or internally written unsafe values cannot bypass the new storage-time validation.</p>Version affected: \u22642.5.45"}], "value": "Affected versions of MISP validate the user-configurable homepage by checking only whether the supplied path begins with /. That check is insufficient because protocol-relative URLs such as //attacker.example also begin with / but resolve to an external origin in browsers.\n\n\nThe vulnerable homepage value can be stored as a user setting and later used by the post-login routing logic. The commit explicitly identifies //attacker.example as a payload that passed validation and was emitted to the Location header after login.\n\nThe fix introduces a shared InternalRedirectValidator that rejects URLs containing a host, scheme, userinfo, unsafe leading // or /\\, malformed URLs, and control characters. It also revalidates homepage settings on read so legacy or internally written unsafe values cannot bypass the new storage-time validation.\n\nVersion affected: \u22642.5.45"}], "impacts": [{"capecId": "CAPEC-178", "descriptions": [{"lang": "en", "value": "CAPEC-178 Cross-Site Flashing"}]}], "metrics": [{"cvssV4_0": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "LOW", "attackRequirements": "NONE", "attackVector": "NETWORK", "baseScore": 5.1, "baseSeverity": "MEDIUM", "privilegesRequired": "LOW", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "LOW", "userInteraction": "PASSIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-601", "description": "CWE-601 URL Redirection to Untrusted Site ('Open Redirect')", "lang": "en", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-20", "description": "CWE-20 Improper Input Validation", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "5a6e4751-2f3f-4070-9419-94fb35b644e8", "shortName": "CIRCL", "dateUpdated": "2026-09-07T09:59:34.850Z"}, "references": [{"tags": ["patch"], "url": "https://github.com/MISP/MISP/commit/bd454f65a"}], "source": {"discovery": "UNKNOWN"}, "title": "MISP User Homepage Validation Allows Authenticated Open Redirect via Protocol-Relative URL", "x_generator": {"engine": "Vulnogram 0.2.0"}}}}

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