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    CVE-2026-9546

    A vulnerability in libcurl caused the HTTP `Referer:` header to persist even when explicitly cleared. While the documentation states that passing NULL to `CURLOPT_REFERER` suppresses the header, the option failed to clear the internal state. As a result the previous referrer string was erroneously reused and sent in subsequent requests, potentially leaking sensitive information to unintended servers.

    Published:Jul 3, 2026
    Last Modified:Jul 7, 2026
    EPS:Jul 3, 2026
    EPSS Score:0.00206
    CVSS Score:7.5

    Affected Products

    Vendor
    Curl
    Product
    Curl

    Exploits

    https://hackerone.com/reports/3754343https://hackerone.com/reports/3754343

    Related CVEs

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    CVE-2026-80229 (CVSS 7.5) — When performing transfers via libcurl’s multi interface, pooled TLS connections can outlive their originating …
    CVE-2026-19931 (CVSS 9.8) — A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authent…
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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