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: 0.5% (43rd percentile of EPSS-scored CVEs). 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: 0.5%CVSS: 9.3Exploit: None knownExposed services: Not assessed

A fix is available — apply it.

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
9.3CRITICALmedium confidence
EG Risk
42
EG Risk 42/100CISA SSVC

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%
Exploitation1% × 40%
Automatability0% × 15%
CISA SSVC: Track at low or medium mission impact; Track* at high (mission-essential systems).
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.5%
EPSS %ILE
44th
KEV
Not listed

CISA SSVCTrack at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Mission impact is CISA's Mission & Well-being decision point, and only you can judge it: high means the affected system is essential to your organisation's mission, or its compromise could cause irreversible harm to people. CISA's decision table

Published

August 18, 2026

Last Modified

September 8, 2026

Advisory Details (3)

Auto-updated Oct 3, 2026
Patch available. Sources: github_release, github.
generic

Version 1.8.40 - MyBB

https://mybb.com/versions/1.8.40
githubMentions a patch (unverified)

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 11× in last 7d / 49× 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. 2026-10-09 20:07 UTCEPSS rescore
  2. 2026-10-08 17:12 UTCEPSS rescore
  3. 2026-10-07 23:48 UTCEPSS rescore
  4. 2026-10-06 17:07 UTCEG score recompute
  5. 2026-10-06 15:18 UTCEPSS rescore
  6. 2026-10-06 08:23 UTCEG score recompute
  7. 2026-10-05 17:43 UTCEPSS rescore
  8. 2026-10-05 01:56 UTCEG score recompute
  9. 2026-10-04 23:22 UTCEPSS rescore
  10. 2026-10-03 17:39 UTCEG score recompute
  11. 2026-10-03 14:25 UTCEPSS rescore
  12. 2026-10-02 19:06 UTCEG score recompute
  13. 2026-10-02 01:28 UTCEG score recompute
  14. 2026-10-01 19:50 UTCEPSS rescore
  15. 2026-09-30 20:50 UTCEG score recompute
  16. 2026-09-30 15:03 UTCEPSS rescore
  17. 2026-09-30 09:48 UTCEG score recompute
  18. 2026-09-28 21:56 UTCEG score recompute
  19. 2026-09-27 16:18 UTCEG score recompute
  20. 2026-09-27 13:48 UTCEPSS rescore
  21. 2026-09-27 07:56 UTCEG score recompute
  22. 2026-09-26 15:58 UTCEPSS rescore
  23. 2026-09-24 16:05 UTCEG score recompute
  24. 2026-09-23 20:20 UTCEG score recompute
  25. 2026-09-23 17:53 UTCEPSS rescore
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  1. 2026-09-22 20:26 UTCEG score recompute
  2. 2026-09-21 22:25 UTCEG score recompute
  3. 2026-09-20 22:27 UTCEG score recompute
  4. 2026-09-20 20:15 UTCEPSS rescore
  5. 2026-09-19 18:44 UTCEG score recompute
  6. 2026-09-18 21:51 UTCEG score recompute
  7. 2026-09-18 19:28 UTCEPSS rescore
  8. 2026-09-17 21:51 UTCEG score recompute
  9. 2026-09-17 19:31 UTCEPSS rescore
  10. 2026-09-16 15:08 UTCEG score recompute
  11. 2026-09-16 14:08 UTCEPSS rescore
  12. 2026-09-16 10:08 UTCEG score recompute
  13. 2026-09-16 05:15 UTCEPSS rescore
  14. 2026-09-15 04:11 UTCEG score recompute
  15. 2026-09-13 20:22 UTCEG score recompute
  16. 2026-09-13 16:47 UTCEPSS rescore
  17. 2026-09-12 17:01 UTCEG score recompute
  18. 2026-09-12 15:01 UTCEPSS rescore
  19. 2026-09-11 17:37 UTCEG score recompute
  20. 2026-09-11 14:53 UTCEPSS rescore
  21. 2026-09-11 13:14 UTCEG score recompute
  22. 2026-09-11 09:37 UTCEPSS rescore
  23. 2026-09-10 13:04 UTCEG score recompute
  24. 2026-09-10 09:34 UTCEPSS rescore
  25. 2026-09-09 03:26 UTCEG score recompute
  26. 2026-09-08 22:00 UTCEPSS rescore
  27. 2026-09-07 16:08 UTCEG score recompute
  28. 2026-09-07 16:01 UTCEPSS rescore
  29. 2026-09-06 15:22 UTCEG score recompute
  30. 2026-09-06 13:47 UTCEPSS rescore
  31. 2026-09-05 15:50 UTCEG score recompute
  32. 2026-09-04 15:39 UTCEG score recompute
  33. 2026-09-04 07:48 UTCEG score recompute
  34. 2026-09-04 05:06 UTCEPSS rescore
  35. 2026-09-02 16:49 UTCEG score recompute
  36. 2026-09-02 14:12 UTCEPSS rescore
  37. 2026-09-01 17:17 UTCEG score recompute
  38. 2026-09-01 13:54 UTCEPSS rescore
  39. 2026-08-30 23:00 UTCEG score recompute
  40. 2026-08-30 19:17 UTCEPSS rescore
  41. 2026-08-30 03:25 UTCEG score recompute
  42. 2026-08-30 01:22 UTCEPSS rescore
  43. 2026-08-29 03:52 UTCEG score recompute
  44. 2026-08-28 21:41 UTCEPSS rescore
  45. 2026-08-27 14:46 UTCEG score recompute
  46. 2026-08-27 14:25 UTCEPSS rescore
  47. 2026-08-26 14:52 UTCEG score recompute
  48. 2026-08-26 14:46 UTCEPSS rescore
  49. 2026-08-25 15:08 UTCEG score recompute
  50. 2026-08-25 13:49 UTCEPSS rescore
  51. 2026-08-24 15:41 UTCEG score recompute
  52. 2026-08-24 11:43 UTCEG score recompute
  53. 2026-08-23 00:34 UTCEG score recompute
  54. 2026-08-23 00:19 UTCEPSS rescore
  55. 2026-08-22 01:08 UTCEG score recompute
  56. 2026-08-21 23:49 UTCEPSS rescore
  57. 2026-08-21 01:45 UTCEG score recompute
  58. 2026-08-20 22:55 UTCEPSS rescore
  59. 2026-08-19 18:15 UTCEG score recompute
  60. 2026-08-19 17:04 UTCEPSS rescore
  61. 2026-08-18 18:24 UTCEG score recompute
  62. 2026-08-18 18:08 UTCEG score recompute
  63. 2026-08-18 16:27 UTCEG score recompute
  64. 2026-08-18 16:12 UTCEG score recompute
  65. 2026-08-18 16:09 UTCMITRE cvelistV5first tracked

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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 on August 18, 2026, with the most recent update on September 8, 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 0.5% probability of exploitation in the next 30 days (44th percentile of EPSS-scored CVEs).
What is the CVSS score of CVE-2026-45118?
CVE-2026-45118 has a CVSS base score of 9.3 (a secondary CVSS source that NVD displays; NVD's own analysis pending).
How do I remediate CVE-2026-45118?
A fix for CVE-2026-45118 is available: update to the fixed version the vendor names in its advisory.

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