{"id":"CVE-2026-45125","title":"MyBB is free and open source forum software","summary":"MyBB is free and open source forum software. Prior to 1.8.40, the Email User controller does not sanitize sender names correctly, resulting in mail header injection. member.php?action=do_emailuser accepts the fromname HTTP parameter for …","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N","cwe":["CWE-93"],"published":"2026-08-18","updated":"2026-09-08","sourceUpdated":"2026-09-08T21:02:26.047","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-45125","references":[{"url":"https://github.com/mybb/mybb/commit/5046c56b515d4593297a4f65b0c6ccb0b55baa01","label":"security-advisories@github.com"},{"url":"https://github.com/mybb/mybb/releases/tag/mybb_1840","label":"security-advisories@github.com"},{"url":"https://github.com/mybb/mybb/security/advisories/GHSA-f626-53q9-pqm9","label":"security-advisories@github.com"},{"url":"https://mybb.com/versions/1.8.40","label":"security-advisories@github.com"}],"tags":["nvd"],"epss":0.00302,"epssPercentile":0.23109,"ingestedAt":"2026-09-08T21:11:12.280Z","slug":"CVE-2026-45125","body":"## Overview\n\nMyBB is free and open source forum software. Prior to 1.8.40, the Email User controller does not sanitize sender names correctly, resulting in mail header injection. member.php?action=do_emailuser accepts the fromname HTTP parameter for guests or the stored username for authenticated users when the cansendemail group permission is enabled. When mail_handler is set to the default PHP mail value, the sender name is used without sanitization in Return-Path and Reply-To headers, allowing arbitrary headers to be injected with CRLF sequences. This issue is fixed in version 1.8.40.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}