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    CVE-2025-53859

    NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during the NGINX SMTP authentication process and requires the attacker to make preparations against the target system to extract the leaked data. The issue affects NGINX only if (1) it is built with the ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method "none," and (3) the authentication server returns the "Auth-Wait" response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

    Published:Aug 13, 2025
    Last Modified:Nov 4, 2025
    EPS:Aug 13, 2025
    EPSS Score:0.00101
    CVSS Score:3.7

    Affected Products

    Vendor
    F5
    Product
    Nginx Open Source
    Vendor
    F5
    Product
    Nginx Plus
    Vendor
    Nginx
    Product
    Nginx

    Exploits

    No exploit reference

    Common Weakness Enumeration

    CWE-125 Out-of-bounds Read

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-540 Overread Buffers

    Related CVEs

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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