{"id":"CVE-2026-45364","state":"PUBLISHED","title":"Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation","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.","publishedAt":"2026-05-28T21:34:51.446Z","updatedAt":"2026-05-29T19:05:38.845Z","severity":{"score":7.3,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L","source":"GitHub_M"},"assigner":"GitHub_M","products":["better-auth better-auth"],"affected":[{"vendor":"better-auth","product":"better-auth","versions":[{"version":"< 1.4.17","status":"affected"},{"version":">= 1.5.0-beta.1, < 1.5.0-beta.9","status":"affected"}]}],"references":["https://github.com/better-auth/better-auth/security/advisories/GHSA-p6v2-xcpg-h6xw","https://github.com/better-auth/better-auth/pull/7470","https://github.com/better-auth/better-auth/pull/7509","https://github.com/better-auth/better-auth/commit/43e719bcc0c223c7079fa0c611a9cf7ea1188254","https://github.com/better-auth/better-auth/commit/57af0f7b910dcf7b1a5c0615d10b9bd56bb69bef"],"weaknesses":["CWE-307"],"ingestedAt":"2026-10-29T20:12:07.131Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/45xxx/CVE-2026-45364.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-45364","state":"PUBLISHED","datePublished":"2026-05-28T21:34:51.446Z","dateUpdated":"2026-05-29T19:05:38.845Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-05-12T00:51:29.085Z"},"containers":{"cna":{"title":"Better Auth: Rate limiter keys IPv6 addresses individually and is bypassable via prefix rotation","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"better-auth","product":"better-auth","versions":[{"version":"< 1.4.17","status":"affected"},{"version":">= 1.5.0-beta.1, < 1.5.0-beta.9","status":"affected"}]}],"references":[{"url":"https://github.com/better-auth/better-auth/security/advisories/GHSA-p6v2-xcpg-h6xw","name":"https://github.com/better-auth/better-auth/security/advisories/GHSA-p6v2-xcpg-h6xw","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/better-auth/better-auth/pull/7470","name":"https://github.com/better-auth/better-auth/pull/7470","tags":["x_refsource_MISC"]},{"url":"https://github.com/better-auth/better-auth/pull/7509","name":"https://github.com/better-auth/better-auth/pull/7509","tags":["x_refsource_MISC"]},{"url":"https://github.com/better-auth/better-auth/commit/43e719bcc0c223c7079fa0c611a9cf7ea1188254","name":"https://github.com/better-auth/better-auth/commit/43e719bcc0c223c7079fa0c611a9cf7ea1188254","tags":["x_refsource_MISC"]},{"url":"https://github.com/better-auth/better-auth/commit/57af0f7b910dcf7b1a5c0615d10b9bd56bb69bef","name":"https://github.com/better-auth/better-auth/commit/57af0f7b910dcf7b1a5c0615d10b9bd56bb69bef","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"LOW","baseScore":7.3,"baseSeverity":"HIGH","confidentialityImpact":"LOW","integrityImpact":"LOW","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-307","lang":"en","description":"CWE-307: Improper Restriction of Excessive Authentication Attempts","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-05-28T21:34:51.446Z"},"source":{"advisory":"GHSA-p6v2-xcpg-h6xw","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-29T19:05:14.121201Z","id":"CVE-2026-45364","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-29T19:05:38.845Z"}}]}}}