{"action":"Upgrade s9y/serendipity to 2.6.0 or later.","affected":[{"fixed":"2.6.0","introduced":"0"}],"component":"s9y/serendipity","cve_ids":["CVE-2026-39971"],"ecosystem":"Packagist","epss":0.00302,"exploited":false,"fixed_versions":["2.6.0"],"ghsa_id":"GHSA-458g-q4fh-mj6r","id":"tcs_01M5KETMRH5ARSQJQZ0WQPRTPZ","modified_at":"2026-05-05T16:00:57.024336Z","published_at":"2026-04-14T22:32:38Z","references":["https://osv.dev/vulnerability/GHSA-458g-q4fh-mj6r","https://github.com/s9y/Serendipity/security/advisories/GHSA-458g-q4fh-mj6r","https://nvd.nist.gov/vuln/detail/CVE-2026-39971","https://github.com/s9y/Serendipity","https://github.com/s9y/Serendipity/releases/tag/2.6.0"],"severity":{"label":"high","score":7.2},"sources":[{"source":"osv","source_id":"GHSA-458g-q4fh-mj6r","url":"https://osv.dev/vulnerability/GHSA-458g-q4fh-mj6r"}],"summary":"Serendipity has a Host Header Injection allows SMTP header injection via unvalidated HTTP_HOST in Message-ID email header"}