CVE-2026-45125

Published: Aug 18, 2026Modified: Sep 8, 2026Deferred

5.3

Vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Exploitability: 3.9 / Impact: 1.4

Source: security-advisories@github.com (Secondary)

Description

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 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.

Related CWEs

CWE-93

Improper Neutralization of CRLF Sequences ('CRLF Injection')

The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs.

References (4)

https://github.com/mybb/mybb/commit/5046c56b515d4593297a4f65b0c6ccb0b55baa01

Source: security-advisories@github.com

https://github.com/mybb/mybb/releases/tag/mybb_1840

Source: security-advisories@github.com

https://github.com/mybb/mybb/security/advisories/GHSA-f626-53q9-pqm9

Source: security-advisories@github.com

https://mybb.com/versions/1.8.40

Source: security-advisories@github.com

Timeline

No history available yet.