CVE-2026-45120

MEDIUMPre-NVD 5.45.4—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.4 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.2%, top 87% 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
5.4EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 5.4Exploit: 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 calendar module does not verify private event status consistently, allowing users with viewing and moderation permissions to access and moderate private events. The private-event check used by get_events() in inc/functions_calendar.php and the event action is missing from the remaining calendar.php actions, despite the limited-access behavior described in inc/languages/english/calendar.lang.php. This issue is fixed in version 1.8.40.

CVSS v3
5.4
EG Score
5.4(medium)
EG Risk
24(Track)
EG Risk 24/100SSVC: 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
Severity54% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
13%
KEV
Not listed

Published

August 18, 2026

Last Modified

August 18, 2026

Advisory Details (4)

Auto-updated Aug 18, 2026
Patch available. Sources: github, github_commit, github_release.
generic

Version 1.8.40 - MyBB

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

mybb_1840

Patch available: mybb/mybb mybb_1840

https://github.com/mybb/mybb/releases/tag/mybb_1840
github_commit Patch Available

commit c077e6c29755 (mybb/mybb)

Patch available: mybb/mybb mybb_1840 (contains commit c077e6c29755)

https://github.com/mybb/mybb/commit/c077e6c29755187c4df78a1e674dd61bc55701b3
github Patch Available

Insufficient authorization for private calendar events · Advisory · mybb/mybb · GitHub

https://github.com/mybb/mybb/security/advisories/GHSA-c2hm-g9w6-pv6x

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 11× in last 7d / 19× 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. 2026-08-27 14:25 UTCEPSS rescore
  2. 2026-08-27 02:08 UTCEG score recompute
  3. 2026-08-26 14:46 UTCEPSS rescore
  4. 2026-08-26 01:10 UTCEG score recompute
  5. 2026-08-25 13:49 UTCEPSS rescore
  6. 2026-08-25 00:12 UTCEG score recompute
  7. 2026-08-23 23:14 UTCEG score recompute
  8. 2026-08-23 00:19 UTCEPSS rescore
  9. 2026-08-22 22:16 UTCEG score recompute
  10. 2026-08-21 23:49 UTCEPSS rescore
  11. 2026-08-21 21:18 UTCEG score recompute
  12. 2026-08-20 22:55 UTCEPSS rescore
  13. 2026-08-19 19:22 UTCEG score recompute
  14. 2026-08-19 17:04 UTCEPSS rescore
  15. 2026-08-18 18:24 UTCEG score recompute
  16. 2026-08-18 17:59 UTCEG score recompute
  17. 2026-08-18 16:27 UTCEG score recompute
  18. 2026-08-18 15:59 UTCEG score recompute
  19. 2026-08-18 15:59 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-45120?
CVE-2026-45120 is a medium vulnerability published on August 18, 2026. MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not verify private event status consistently, allowing users with viewing and moderation permissions to access and moderate private events. The private-event check used by getevents() in inc/functionscalendar.php…
When was CVE-2026-45120 disclosed?
CVE-2026-45120 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-2026-45120 actively exploited?
CVE-2026-45120 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 87.3% of all scored CVEs.
What is the CVSS score of CVE-2026-45120?
CVE-2026-45120 has a CVSS v3 base score of 5.4 (NVD).
How do I remediate CVE-2026-45120?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-45120, 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.

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