CVE-2026-45118 MyBB: Contact page reflected XSS
Attackers can inject JavaScript via the contact page redirect parameter, allowing script execution when victims click a link.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-45118?
CVE-2026-45118 is a critical cross-site scripting vulnerability in mybb, published on 18 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official 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.
Weakness: CWE-83
Which versions are affected by CVE-2026-45118?
How do I fix CVE-2026-45118?
No fix has been published for CVE-2026-45118 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-45118 being exploited?
There is no known exploitation of CVE-2026-45118 in the wild and no public exploit code.
Sources
Also known as GHSA-wf92-5q5h-qr53.