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CVE-2026-45118

9.3 · CRITICAL

MyBB is free and open source forum software.

Published Aug 18, 2026CWE-83EPSS 0.55%

Overview

CVE-2026-45118 is a critical-severity vulnerability. It was published on August 18, 2026 and has a CVSS 3.1 base score of 9.3 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.3, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

MyBB is free and open source forum software. Prior to 1.8.40, the Contact module does not validate a redirect URL or protocol correctly, resulting in an open redirect and reflected JavaScript code injection. contact.php accepts the redirect target from the from HTTP parameter in $mybb->input['from'] or the Referer HTTP header in $_SERVER['HTTP_REFERER'] and passes it to redirect() without sufficient verification. A javascript: URI becomes the target of the `Click here if you don't want to wait any longer` link because $force_redirect is true, allowing script execution when a victim selects the link. This issue is fixed in version 1.8.40.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/mybb/mybb/releases/tag/mybb_1840GitHubgithub.com/mybb/mybb/security/advisories/GHSA-wf92-5q5h-qr53Refmybb.com/versions/1.8.40

How CyberStrike helps

Frequently asked questions

What is CVE-2026-45118?

CVE-2026-45118 is a critical-severity vulnerability. It was published on August 18, 2026 and has a CVSS 3.1 base score of 9.3 (CRITICAL).

How severe is CVE-2026-45118?

This vulnerability has a CVSS 3.1 base score of 9.3, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-45118?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-45118?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-45118 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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