{"id":"CVE-2026-42181","sourceIdentifier":"security-advisories@github.com","published":"2026-05-08T20:16:31.160","lastModified":"2026-06-17T10:47:28.533","vulnStatus":"Deferred","cveTags":[],"descriptions":[{"lang":"en","value":"Lemmy is a link aggregator and forum for the fediverse. Prior to version 0.19.18, Lemmy fetches metadata for user-supplied post URLs and, under the default StoreLinkPreviews image mode, downloads the preview image through local pict-rs. While the top-level page URL is checked against internal IP ranges, the extracted og:image URL is not subject to the same restriction. As a result, an authenticated low-privileged user can submit an attacker-controlled public page whose Open Graph image points to an internal image endpoint. Lemmy will fetch that internal image server-side and store a local thumbnail that can then be served back to users. This issue has been patched in version 0.19.18."}],"affected":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"LemmyNet","product":"lemmy","versions":[{"version":"< 0.19.18","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","baseScore":6.5,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"NONE","availabilityImpact":"NONE"},"exploitabilityScore":2.8,"impactScore":3.6}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-05-11T16:00:57.536211Z","id":"CVE-2026-42181","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-918"}]}],"references":[{"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-h6hf-9846-xwrq","source":"security-advisories@github.com"},{"url":"https://github.com/LemmyNet/lemmy/security/advisories/GHSA-h6hf-9846-xwrq","source":"134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}