CVE-2026-45118
CRITICALDescription
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.
How to fix
No published remediation has been found for this vulnerability's affected products yet.
Mitigation guidance may be in the linked vendor advisories in the References section below.
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CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 31% of all known CVEs.
References
Related Vulnerabilities
Other CWE-83 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2023-37908 | Critical | 9.0 | 1.1% | - | Fix |
| CVE-2025-4615 | High | 7.2 | 0.7% | - | Fix |
| CVE-2023-32070 | Critical | 9.0 | 0.7% | - | - |
| CVE-2022-39262 | Medium | 5.2 | 0.7% | - | Fix |
| CVE-2024-52595 | High | 7.7 | 0.5% | - | Fix |
| CVE-2020-14525 | Low | 3.5 | 0.5% | - | - |
Common questions
How do I fix CVE-2026-45118?
No published fix for CVE-2026-45118 has been found yet. Check the linked vendor advisories for guidance as it becomes available.
Is CVE-2026-45118 being actively exploited?
Not that we know of. CVE-2026-45118 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.38% is the estimated probability that it will be exploited in the next 30 days. That is higher than 31% of all scored CVEs.
How severe is CVE-2026-45118?
CVE-2026-45118 has a CVSS v3 base score of 9.3, rated critical. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-18.