CVE-2021-0259

    Dashboard / Vulnerabilities / CVE-2021-0259

    CVE-2021-0259

    Published: 22 Apr 2021Last Modified: 10 Mar 2026

    Summary:

    Details: Due to a vulnerability in DDoS protection in Juniper Networks Junos OS and Junos OS Evolved on QFX5K Series switches in a VXLAN configuration, instability might be experienced in the underlay network as a consequence of exceeding the default ddos-protection aggregate threshold. If an attacker on a client device on the overlay network sends a high volume of specific, legitimate traffic in the overlay network, due to an improperly detected DDoS violation, the leaf might not process certain L2 traffic, sent by spines in the underlay network. Continued receipt and processing of the high volume traffic will sustain the Denial of Service (DoS) condition. This issue affects: Juniper Networks Junos OS on QFX5K Series: 17.3 versions prior to 17.3R3-S11; 17.4 versions prior to 17.4R3-S5; 18.1 versions prior to 18.1R3-S13; 18.2 versions prior to 18.2R2-S8, 18.2R3-S8; 18.3 versions prior to 18.3R3-S5; 18.4 versions prior to 18.4R1-S8, 18.4R2-S6, 18.4R3-S6; 19.1 versions prior to 19.1R3-S4; 19.2 versions prior to 19.2R1-S6, 19.2R3-S2; 19.3 versions prior to 19.3R3-S2; 19.4 versions prior to 19.4R2-S4, 19.4R3-S1; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2; 20.3 versions prior to 20.3R1-S2, 20.3R2. Juniper Networks Junos OS Evolved on QFX5220: All versions prior to 20.3R2-EVO.

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: N/A

    Events:

    Introduced- None
    Fixed -None

    Affected versions

    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
    CVE-2021-0259 | CVE-DB