CVE-2026-45364

7.3 HIGH 0.3% exploit odds Fix listed Other Library

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. Limited direct impact.
Exploit odds: 0.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-05-28 22:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-07-21 10:10 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.3% in the next 30 days (EPSS).
Severity: 7.3 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-05-28 22:17 UTC
Last modified: 2026-07-21 10:10 UTC
Exploit probability: 0.3% · EPSS, next 30 days
Weakness: CWE-307
Record status: Deferred

Attack profile CVSS 3.1 · 7.3

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: Low

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-45364.md and follow it. Check whether this project is affected by CVE-2026-45364. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record