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    CVE-2026-45121

    MyBB is free and open source forum software. Prior to 1.8.40, the calendar module does not check permissions consistently when listing calendars, allowing authenticated users to access titles of calendars that are otherwise inaccessible. The affected calendar-selection paths in calendar.php perform permission checks against an invalid calendar context before returning calendar titles. The uniquely identifying implementation details include titles of inaccessible calendars, and invalid calendar permission context. This issue is fixed in version 1.8.40.

    Published:Aug 18, 2026
    Last Modified:Aug 18, 2026
    EPS:Aug 18, 2026
    EPSS Score:
    CVSS Score:4.3

    Affected Products

    Vendor
    Mybb
    Product
    Mybb

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-863 Incorrect Authorization

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

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    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High