Vulnerability in better-auth (CVE-2026-45364)
Summary
Vulnerability in better-auth (CVE-2026-45364). Risk of unauthorized operations or information disclosure. Exploitable via normalizeIP. Mitigation: upgrade to 1.5.0-beta.9 or later.
Original description
The description as published by the source.
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.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-45364 has been found in better-auth.
Attackers can target a specific entry point like normalizeIP over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.3/10.
What to do: upgrade better-auth to 1.5.0-beta.9 or later.
If unsure, ask your IT team or search "better-auth CVE-2026-45364" on the vendor's site.
CVE-2026-45364 (better-auth) — CWE-307 / CVSS v3 7.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: normalizeIP / getIp / onRequestRateLimit / advanced.ipAddress.ipv6Subnet
Patched: 1.5.0-beta.9 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-307) exists in better-auth. Attackers reach the vulnerable code path via normalizeIP without authentication.
Check the vendor advisory for the affected versions of better-auth. Attack surface: normalizeIP / getIp / onRequestRateLimit / advanced.ipAddress.ipv6Subnet.
Severity: High (CVSS 7.3/10). Risk of unauthorized operations or information disclosure.
Update to 1.5.0-beta.9.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'better-auth' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'better-auth' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
better-authを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade better-auth to 1.5.0-beta.9ステージング環境で 1.5.0-beta.9 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- patch github.com
- patch github.com
- patch github.com
- web github.com