{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-63115", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-07-15T16:54:55.816Z", "datePublished": "2026-10-30T21:33:55.894Z", "dateUpdated": "2026-10-30T21:33:55.894Z"}, "containers": {"cna": {"title": "ActivityPub Undo handler can unfollow or remove reposts on behalf of other accounts", "problemTypes": [{"descriptions": [{"cweId": "CWE-290", "lang": "en", "description": "CWE-290: Authentication Bypass by Spoofing", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-345", "lang": "en", "description": "CWE-345: Insufficient Verification of Data Authenticity", "type": "CWE"}]}, {"descriptions": [{"cweId": "CWE-863", "lang": "en", "description": "CWE-863: Incorrect Authorization", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc"}, {"name": "https://github.com/TryGhost/ActivityPub/pull/1929", "tags": ["x_refsource_MISC"], "url": "https://github.com/TryGhost/ActivityPub/pull/1929"}, {"name": "https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e", "tags": ["x_refsource_MISC"], "url": "https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e"}, {"name": "https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6", "tags": ["x_refsource_MISC"], "url": "https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6"}], "affected": [{"vendor": "TryGhost", "product": "ActivityPub", "versions": [{"version": ">= 1.0.0, < 1.2.6", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-10-30T21:33:55.894Z"}, "descriptions": [{"lang": "en", "value": "ActivityPub is a multi-tenant ActivityPub server for Ghost, built with Fedify. From 1.0.0 until 1.2.6, the `Undo` handler allows a remote federated server to cause the service to act on a `follow` or `repost` as though the activity came from a different account. This permits removal of an existing `follow` relationship or `repost` belonging to another account without that account's involvement. No private data is exposed and content is not modified; the affected relationships can be re-established. Services proxying to Ghost's hosted ActivityPub server have already been updated, while self-hosted services require an updated image and redeployment. This issue is fixed in version 1.2.6."}], "source": {"advisory": "GHSA-mm4q-93gr-5mwc", "discovery": "UNKNOWN"}}}}

{}

{"affected": [{"affectedData": [{"product": "ActivityPub", "vendor": "TryGhost", "versions": [{"status": "affected", "version": ">= 1.0.0, < 1.2.6"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "ActivityPub is a multi-tenant ActivityPub server for Ghost, built with Fedify. From 1.0.0 until 1.2.6, the `Undo` handler allows a remote federated server to cause the service to act on a `follow` or `repost` as though the activity came from a different account. This permits removal of an existing `follow` relationship or `repost` belonging to another account without that account's involvement. No private data is exposed and content is not modified; the affected relationships can be re-established. Services proxying to Ghost's hosted ActivityPub server have already been updated, while self-hosted services require an updated image and redeployment. This issue is fixed in version 1.2.6."}], "id": "CVE-2026-63115", "lastModified": "2026-10-30T22:16:57.963", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 5.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 1.4, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-10-30T22:16:57.963", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/TryGhost/ActivityPub/commit/1526f540b983da97750b380868a210e6cdfb985e"}, {"source": "security-advisories@github.com", "url": "https://github.com/TryGhost/ActivityPub/pull/1929"}, {"source": "security-advisories@github.com", "url": "https://github.com/TryGhost/ActivityPub/releases/tag/v1.2.6"}, {"source": "security-advisories@github.com", "url": "https://github.com/TryGhost/ActivityPub/security/advisories/GHSA-mm4q-93gr-5mwc"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-290"}, {"lang": "en", "value": "CWE-345"}, {"lang": "en", "value": "CWE-863"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{}