VULNERABILITY INTELLIGENCE
CVE-2026-45123
CVSS score4.3 MEDIUM
EPSS probability0.37%
CISA KEVNot currently listed
Published2026-08-18
Last modified2026-09-08
CVSS vectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
Description
MyBB is free and open source forum software. Prior to 1.8.40, the remote requests feature does not correctly handle IPv6 addresses, resulting in a server-side request forgery vulnerability. The default disallowed remote hosts list does not include IPv6 addresses. Verification in fetch_remote_file() fails open when get_ip_by_hostname() returns no result because that function does not return IPv6 results, allowing a crafted remote target to bypass the host restriction. The uniquely identifying implementation details include fail-open verification, and inc/functions.php. This issue is fixed in version 1.8.40.
Weakness classification
- security-advisories@github.com: CWE-918