CVE-2026-121506

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    CVE-2026-121506

    Published: 3 Nov 2026Last Modified: 5 Nov 2026

    Summary: Out-of-bounds Write in NTPsec

    Details: An out-of-bounds read and write in NTS client extension field parsing (extens_client_recv) in NTPsec before 1.2.5 allows a remote attacker who can send NTP server-mode replies to an NTS client to corrupt heap memory and crash ntpd, and, combined with the NTS-KE client out-of-bounds read fixed in 1.2.4, to bypass NTS authentication and set the client's time, via an NTS Authenticator and Encrypted Extension Fields field whose nonce length exceeds the field.

    References: https://gitlab.com/NTPsec/ntpsec/-/work_items/902, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/121xxx/CVE-2026-121506.json, https://nvd.nist.gov/vuln/detail/CVE-2026-121506, https://gitlab.com/NTPsec/ntpsec/-/commit/0a36941e499d533dfbc3fb6b1fcd8c367679d719, https://gitlab.com/NTPsec/ntpsec

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 79cd18fc56fc902c3a7fd78bcc32ee72f52eb396
    Fixed -42b5703303c8c7e6513f3a119cfab670924dd7be

    Affected versions

    NTPsec_1_2_4

    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-2026-121506 | CVE-DB