{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-42180", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-04-25T01:53:21.582Z", "datePublished": "2026-05-08T19:29:04.132Z", "dateUpdated": "2026-05-08T19:29:04.132Z"}, "containers": {"cna": {"title": "Lemmy: SSRF in /api/v3/post via Webmention dispatch", "problemTypes": [{"descriptions": [{"cweId": "CWE-918", "lang": "en", "description": "CWE-918: Server-Side Request Forgery (SSRF)", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 6.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L", "version": "3.1"}}], "references": [{"name": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948"}, {"name": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.18", "tags": ["x_refsource_MISC"], "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.18"}], "affected": [{"vendor": "LemmyNet", "product": "lemmy", "versions": [{"version": "< 0.19.18", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-05-08T19:29:04.132Z"}, "descriptions": [{"lang": "en", "value": "Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy allows an authenticated low-privileged user to create a link post through POST /api/v3/post. When a post is created in a public community, the backend asynchronously sends a Webmention to the attacker-controlled link target. The submitted URL is checked for syntax and scheme, but the audited code path does not reject loopback, private, or link-local destinations before the Webmention request is issued. This lets a normal user trigger server-side HTTP requests toward internal services. This issue has been patched in version 0.19.18."}], "source": {"advisory": "GHSA-3jvj-v6w2-h948", "discovery": "UNKNOWN"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy allows an authenticated low-privileged user to create a link post through POST /api/v3/post. When a post is created in a public community, the backend asynchronously sends a Webmention to the attacker-controlled link target. The submitted URL is checked for syntax and scheme, but the audited code path does not reject loopback, private, or link-local destinations before the Webmention request is issued. This lets a normal user trigger server-side HTTP requests toward internal services. This issue has been patched in version 0.19.18."}], "id": "CVE-2026-42180", "lastModified": "2026-05-08T20:16:31.023", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "LOW", "baseScore": 6.3, "baseSeverity": "MEDIUM", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.4, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-05-08T20:16:31.023", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/releases/tag/0.19.18"}, {"source": "security-advisories@github.com", "url": "https://github.com/LemmyNet/lemmy/security/advisories/GHSA-3jvj-v6w2-h948"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-918"}], "source": "security-advisories@github.com", "type": "Primary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,0.19.18)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "lemmy", "source": "cna", "vendor": "LemmyNet"}, "product": "lemmy", "vendor": "lemmynet"}], "created": "2026-05-08T22:00:15.884226+00:00", "updated": "2026-05-08T22:30:18.071220+00:00", "vendors": ["lemmynet", "lemmynet$PRODUCT$lemmy"]}