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    CVE-2026-33393

    Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the `allowed_spam_host_domains` check used `String#end_with?` without domain boundary validation, allowing domains like `attacker-example.com` to bypass spam protection when `example.com` was allowlisted. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 require exact match or proper subdomain match (preceded by `.`) to prevent suffix-based bypass of `newuser_spam_host_threshold`. No known workarounds are available.

    Published:Mar 19, 2026
    Last Modified:Mar 25, 2026
    EPS:Mar 19, 2026
    EPSS Score:0.00028
    CVSS Score:4.3

    Affected Products

    Vendor
    Discourse
    Product
    Discourse

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-284 Improper Access Control

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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