Is CVE-2026-45364 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-45364 being exploited in the wild.

How severe is CVE-2026-45364?

High severity, with a CVSS score of 7.3, published 28 May 2026.

Which products and versions are affected?

better-auth (npm) SEMVER:introduced=0,fixed=1.4.17.

Is there a fix for CVE-2026-45364?

Yes. better-auth (npm): upgrade to 1.4.17 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-45364 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-45364?

Check whether you run better-auth (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-45364: Better Auth rate limit bypass via IPv6 address rotation and encoding

CVE-2026-45364 · Severity: high · CVSS 7.3 · Published 2026-05-28

Better Auth is an authentication library for web applications. A flaw in its rate-limiting system allows attackers using IPv6 connections to bypass security limits on sensitive actions like signing in or resetting passwords. This could allow an attacker to perform unlimited login attempts or send excessive automated emails, potentially leading to account takeovers or service abuse.

Technologies: better-auth (npm). Vendors: npm.

Quick answers

Is CVE-2026-45364 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-45364 being exploited in the wild.
How severe is CVE-2026-45364?: High severity, with a CVSS score of 7.3, published 28 May 2026.
Which products and versions are affected?: better-auth (npm) SEMVER:introduced=0,fixed=1.4.17.
Is there a fix for CVE-2026-45364?: Yes. better-auth (npm): upgrade to 1.4.17 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-45364 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-45364?: Check whether you run better-auth (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

better-auth (npm): upgrade to 1.4.17 or later
```
npm install better-auth@1.4.17
```

Technical details

The Better Auth HTTP rate limiter improperly keyed requests using the verbatim textual IP address from headers like 'x-forwarded-for'. Because IPv6 allows for multiple textual representations of the same address and ISPs typically assign large address blocks (prefixes) to single users, attackers could rotate through billions of source addresses or vary the string encoding to bypass per-IP counters. This affects critical endpoints including sign-in, sign-up, and password resets. The fix introduces IP normalization and applies a default /64 prefix mask to treat entire subnets as a single client.

Affected products

better-auth better-auth < 1.4.17, >= 1.5.0-beta.1 < 1.5.0-beta.9

Identifiers

CVE-2026-45364
GHSA-p6v2-xcpg-h6xw

Timeline

2026-05-11: disclosed
2026-05-15: advisory
2026-05-28: kev added: NVD publication date

References

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