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CVE-2026-45120— MyBB: Insufficient authorization for private calendar events

Quick assessment

Affected
mybb mybb
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

MyBB是MyBB组织开源的一套用PHP和MySQL开发的免费且基于Web的论坛软件。该软件具有简单易用、支持多国语言、可扩展等特点。 MyBB 1.8.40之前版本存在授权问题漏洞，该漏洞源于inc/functions_calendar.php中get_events()函数对私人事件状态的验证不一致，且calendar.php中缺少事件操作检查，导致具有查看和审核权限的用户能够访问和审核私人事件。

CVSS 5.4 · Medium EPSS 0.22% · P13

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage

Affected Version Matrix 1

VendorProduct Version RangeStatus
mybb mybb < 1.8.40 affected
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I. Basic Information for CVE-2026-45120

Vulnerability Information
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Vulnerability Title
MyBB: Insufficient authorization for private calendar events
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过用户控制密钥绕过授权机制
Source: CVE Program / CVE List V5
Vulnerability Title
MyBB 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MyBB是MyBB组织开源的一套用PHP和MySQL开发的免费且基于Web的论坛软件。该软件具有简单易用、支持多国语言、可扩展等特点。 MyBB 1.8.40之前版本存在授权问题漏洞，该漏洞源于inc/functions_calendar.php中get_events()函数对私人事件状态的验证不一致，且calendar.php中缺少事件操作检查，导致具有查看和审核权限的用户能够访问和审核私人事件。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mybb mybb < 1.8.40 -

II. Public POCs for CVE-2026-45120

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III. Intelligence Information for CVE-2026-45120

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Patches & Fixes for CVE-2026-45120 (2)

Vendor Advisories for CVE-2026-45120 (1)

Vendor Pages for CVE-2026-45120 (1)

Same Patch Batch · mybb · 2026-08-18 · 18 CVEs total

CVE-2026-45117 9.8 CRITICAL MyBB: Installer database configuration RCE
CVE-2026-45118 9.3 CRITICAL MyBB: Contact page reflected XSS
CVE-2026-45115 8.7 HIGH MyBB: Buddy/ignore list username XSS
CVE-2026-45116 8.7 HIGH MyBB: Profile field type confusion XSS
CVE-2026-46482 5.3 MEDIUM MyBB: Security Question insufficient validation
CVE-2026-45734 5.3 MEDIUM MyBB: Default CAPTCHA missing invalidation
CVE-2026-45125 5.3 MEDIUM MyBB: Email User CRLF injection
CVE-2026-45119 4.6 MEDIUM MyBB: ACP UTF-8 Conversion CSRF
CVE-2026-45129 4.6 MEDIUM MyBB: ACP Recovery Codes CSRF
CVE-2026-45123 4.3 MEDIUM MyBB: IPv6 SSRF
CVE-2026-45122 4.3 MEDIUM MyBB: Insufficient permission check for calendar event move
CVE-2026-45121 4.3 MEDIUM MyBB: Insufficient permission check for calendar select
CVE-2026-45124 4.3 MEDIUM MyBB: Mod CP report resolution missing authorization
CVE-2026-47245 4.3 MEDIUM MyBB: Buddy list corruption
CVE-2026-45126 3.5 LOW MyBB: ACP Questions state CSRF
CVE-2026-45128 3.5 LOW MyBB: ACP Users View Manager default CSRF
CVE-2026-45127 3.5 LOW MyBB: ACP Mass Mail draft resend CSRF

IV. Related Vulnerabilities

Same product: mybb
Same vendor: mybb
Same weakness: CWE-639

V. Comments for CVE-2026-45120

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