CVE-2026-45123
MEDIUM
4,3
Source: [email protected]
Attack Vector: network
Attack Complexity: low
Privileges Required: low
User Interaction: none
Scope: unchanged
Confidentiality: low
Integrity: none
Availability: none
Description
AI Translation Available
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.
918
Server-Side Request Forgery (SSRF)
IncompleteCommon Consequences
Security Scopes Affected:
Confidentiality
Integrity
Access Control
Potential Impacts:
Read Application Data
Execute Unauthorized Code Or Commands
Bypass Protection Mechanism
Applicable Platforms
Technologies:
Web Based, AI/ML, Web Server
https://github.com/mybb/mybb/commit/9cdadbf66f4cef50019f13aaa8e3470ea6535cb7
https://github.com/mybb/mybb/releases/tag/mybb_1840
https://github.com/mybb/mybb/security/advisories/GHSA-56wr-64wx-5g7j
https://mybb.com/versions/1.8.40