{ "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": "2026-09-08T14:49:21.745Z" }, "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": "

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

The 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.

The 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.

Version affected: ≤2.5.45" } ], "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: ≤2.5.45" } ], "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" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-09-08T14:49:13.991856Z", "id": "CVE-2026-86351", "options": [ { "Exploitation": "none" }, { "Automatable": "no" }, { "Technical Impact": "partial" } ], "role": "CISA Coordinator", "version": "2.0.3" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-09-08T14:49:21.745Z" } } ] } }