Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation_CVE-2026-45364

{
    "lastseen": "",
    "description": "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": "2026-05-28T21:34:51.446Z",
    "modified": "2026-05-28T21:34:51.446Z",
    "type": "cve",
    "title": "Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation",
    "source": "GitHub_M",
    "references": "https://github.com/better-auth/better-auth/security/advisories/GHSA-p6v2-xcpg-h6xw\nhttps://github.com/better-auth/better-auth/pull/7470\nhttps://github.com/better-auth/better-auth/pull/7509\nhttps://github.com/better-auth/better-auth/commit/43e719bcc0c223c7079fa0c611a9cf7ea1188254\nhttps://github.com/better-auth/better-auth/commit/57af0f7b910dcf7b1a5c0615d10b9bd56bb69bef",
    "id": "CVE-2026-45364",
    "bulletinFamily": "",
    "cwe": [
        "CWE-307"
    ],
    "cvelist": null,
    "sourceData": "better-auth better-auth < 1.4.17\nbetter-auth better-auth >= 1.5.0-beta.1, < 1.5.0-beta.9",
    "sourceHref": "",
    "cvss": {
        "score": 7.3,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "better-auth",
    "version": "< 1.4.17",
    "vendor": "better-auth",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}