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    CVE-2026-45364

    Better Auth is an authentication and authorization library for TypeScript. Prior to 1.4.17 and 1.5.0-beta.9, Better Auth's HTTP rate limiter keyed each request by the exact textual IP address it received in x-forwarded-for (or the configured IP-bearing header). IPv6 clients controlling a typical /64 allocation could rotate through 2^64 distinct source addresses without exhausting the per-address counter, defeating rate limiting on /sign-in/email, /sign-up/email, /forget-password, and every other path the limiter protects. The same bug allowed a single client to vary the textual encoding of one IPv6 address (uppercase, compression, IPv4-mapped, hex-encoded IPv4-in-IPv6) and produce multiple distinct keys. This vulnerability is fixed in 1.4.17 and 1.5.0-beta.9.

    Published:May 28, 2026
    Last Modified:May 29, 2026
    EPS:May 28, 2026
    EPSS Score:0.0007
    CVSS Score:7.3

    Affected Products

    Vendor
    Better-auth
    Product
    Better Auth

    Exploits

    No exploit reference

    Related CVEs

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    CVE-2026-67333 (CVSS 5.1) — better-auth before 1.6.13 (and pre-release builds 1.7.0-beta.0 through 1.7.0-beta.3) fail to validate the sche…
    CVE-2026-67329 (CVSS 7.1) — @better-auth/stripe versions >= 1.4.11 and < 1.6.21, and >= 1.7.0-beta.0 and < 1.7.0-beta.10, contain an autho…
    CVE-2026-67334 (CVSS 5.1) — better-auth versions before 1.6.11 fail to delete cached sessions when removing users via admin, anonymous, or…
    CVE-2025-71403 (CVSS 7.1) — better-auth versions before 1.1.20 contain a bypass vulnerability in trustedOrigins validation logic affecting…
    CVE-2026-67337 (CVSS 7.1) — better-auth versions before 1.4.9 contain a two-factor authentication bypass vulnerability when session.cookie…
    CVE-2025-71404 (CVSS 5.1) — better-auth versions after v0.0.2 and before 1.1.16 contain a reflected cross-site scripting (XSS) vulnerabili…
    CVE-2026-67327 (CVSS 8.7) — better-auth versions >= 1.1.3 and < 1.6.22 (and pre-release versions >= 1.7.0-beta.0 and < 1.7.0-beta.10) are …
    CVE-2026-67331 (CVSS 8.7) — better-auth SCIM versions from 1.5.0 before 1.7.0-beta.4 fail to bind non-organization SCIM providers to their…

    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