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    CVE-2026-6276

    Using libcurl, when a custom `Host:` header is first set for an HTTP request and a second request is subsequently done using the same *easy handle* but without the custom `Host:` header set, the second request would use stale information and pass on cookies meant for the first host in the second request. Leak them.

    Published:Apr 29, 2026
    Last Modified:May 14, 2026
    EPS:May 13, 2026
    EPSS Score:0.00019
    CVSS Score:7.5

    Affected Products

    Vendor
    Curl
    Product
    Libcurl
    Vendor
    Haxx
    Product
    Curl

    Exploits

    https://hackerone.com/reports/3671818https://hackerone.com/reports/3671818

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-102 Session Sidejacking
    CAPEC-111 JSON Hijacking (aka JavaScript Hijacking)
    CAPEC-117 Interception
    CAPEC-141 Cache Poisoning
    CAPEC-142 DNS Cache Poisoning
    CAPEC-160 Exploit Script-Based APIs
    CAPEC-21 Exploitation of Trusted Identifiers
    CAPEC-383 Harvesting Information via API Event Monitoring
    CAPEC-384 Application API Message Manipulation via Man-in-the-Middle
    CAPEC-385 Transaction or Event Tampering via Application API Manipulation
    CAPEC-386 Application API Navigation Remapping
    CAPEC-387 Navigation Remapping To Propagate Malicious Content
    CAPEC-388 Application API Button Hijacking
    CAPEC-477 Signature Spoofing by Mixing Signed and Unsigned Content
    CAPEC-510 SaaS User Request Forgery
    CAPEC-59 Session Credential Falsification through Prediction
    CAPEC-60 Reusing Session IDs (aka Session Replay)
    CAPEC-65 Sniff Application Code
    CAPEC-75 Manipulating Writeable Configuration Files
    CAPEC-76 Manipulating Web Input to File System Calls
    CAPEC-89 Pharming

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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