CVE-2026-45118

CRITICALPre-NVD 9.39.3—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.3 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 69% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, secondary
9.3EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.3Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.3
EG Score
9.3(medium)
EG Risk
42(Track)
EG Risk 42/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity93% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
31%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 18, 2026

Advisory Details (3)

Auto-updated Aug 23, 2026
Patch available. Sources: github_release, github.
generic

Version 1.8.40 - MyBB

https://mybb.com/versions/1.8.40
github Patch Available

Contact page reflected XSS · Advisory · mybb/mybb · GitHub

https://github.com/mybb/mybb/security/advisories/GHSA-wf92-5q5h-qr53
github_release Patch Available

mybb_1840

Patch available: mybb/mybb mybb_1840

https://github.com/mybb/mybb/releases/tag/mybb_1840

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 12× in last 7d / 17× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-08-25 15:08 UTCEG score recompute
  2. 2026-08-25 13:49 UTCEPSS rescore
  3. 2026-08-24 15:41 UTCEG score recompute
  4. 2026-08-24 11:43 UTCEG score recompute
  5. 2026-08-23 00:34 UTCEG score recompute
  6. 2026-08-23 00:19 UTCEPSS rescore
  7. 2026-08-22 01:08 UTCEG score recompute
  8. 2026-08-21 23:49 UTCEPSS rescore
  9. 2026-08-21 01:45 UTCEG score recompute
  10. 2026-08-20 22:55 UTCEPSS rescore
  11. 2026-08-19 18:15 UTCEG score recompute
  12. 2026-08-19 17:04 UTCEPSS rescore
  13. 2026-08-18 18:24 UTCEG score recompute
  14. 2026-08-18 18:08 UTCEG score recompute
  15. 2026-08-18 16:27 UTCEG score recompute
  16. 2026-08-18 16:12 UTCEG score recompute
  17. 2026-08-18 16:09 UTCMITRE cvelistV5first tracked

Frequently asked(5)

What is CVE-2026-45118?
CVE-2026-45118 is a critical vulnerability published on August 18, 2026. 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…
When was CVE-2026-45118 disclosed?
CVE-2026-45118 was first published in the National Vulnerability Database on August 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-45118 actively exploited?
CVE-2026-45118 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 68.8% of all scored CVEs.
What is the CVSS score of CVE-2026-45118?
CVE-2026-45118 has a CVSS v3 base score of 9.3 (NVD).
How do I remediate CVE-2026-45118?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-45118, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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