CVE-2026-59993

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    CVE-2026-59993

    Published: 30 Oct 2026Last Modified: 8 Nov 2026

    Summary: Picotls has NULL pointer dereference during handshake, when running as a client

    Details: Picotls is a TLS protocol library that allows users select different crypto backends based on their use case. In affected revisions through 44bc503, when picotls is used as a `client-side TLS stack`, a peer can send a `HelloRetryRequest` followed by a `spoofed Hello message` that causes a null-pointer dereference. This can terminate the consuming process, including a process performing other work, resulting in denial of service. This issue is fixed in commit a06ca41.

    References: https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59993.json, https://github.com/h2o/picotls/security/advisories/GHSA-2xcv-h2pg-m99c, https://nvd.nist.gov/vuln/detail/CVE-2026-59993, https://github.com/h2o/picotls/commit/a06ca417a16f9126808bf5cabe6c5e6e0f16ecae, https://github.com/h2o/picotls/pull/608

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: GIT

    Events:

    Introduced- 0
    Fixed -a06ca417a16f9126808bf5cabe6c5e6e0f16ecae

    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-2026-59993 | CVE-DB