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    CVE-2026-75509

    joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.

    Published:Aug 24, 2026
    Last Modified:Aug 25, 2026
    EPS:Aug 24, 2026
    EPSS Score:0.00091
    CVSS Score:6.5

    Affected Products

    Vendor
    Authlib
    Product
    Joserfc

    Exploits

    No exploit reference

    Common Attack Pattern Enumeration and Classification (CAPEC)

    CAPEC-111 JSON Hijacking (aka JavaScript Hijacking)
    CAPEC-141 Cache Poisoning
    CAPEC-142 DNS Cache Poisoning
    CAPEC-148 Content Spoofing
    CAPEC-21 Exploitation of Trusted Identifiers
    CAPEC-218 Spoofing of UDDI/ebXML Messages
    CAPEC-22 Exploiting Trust in Client
    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-459 Creating a Rogue Certification Authority Certificate
    CAPEC-461 Web Services API Signature Forgery Leveraging Hash Function Extension Weakness
    CAPEC-473 Signature Spoof
    CAPEC-476 Signature Spoofing by Misrepresentation
    CAPEC-59 Session Credential Falsification through Prediction
    CAPEC-60 Reusing Session IDs (aka Session Replay)
    CAPEC-665 Exploitation of Thunderbolt Protection Flaws
    CAPEC-667 Bluetooth Impersonation AttackS (BIAS)
    CAPEC-701 Browser in the Middle (BiTM)
    CAPEC-94 Adversary in the Middle (AiTM)

    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