How severe is CVE-2026-45364?

CVE-2026-45364 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2026-45364 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-45364?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-45364 have an EU (EUVD) identifier?

Yes. CVE-2026-45364 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33073.

When was CVE-2026-45364 published?

CVE-2026-45364 was published on 2026-05-28 and last updated on 2026-06-17.

CVE-2026-45364

CVE-2026-45364 is a high-severity vulnerability with a CVSS 3.x base score of 7.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-307.

Key facts

Severity: High (CVSS 3.x base score 7.3)
EPSS exploit prediction: 0% (21st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-33073
Weakness: CWE-307
Published: 2026-05-28
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-45364?: 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.
How severe is CVE-2026-45364?: CVE-2026-45364 has a CVSS 3.x base score of 7.3, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2026-45364 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (21st percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-45364?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-45364 have an EU (EUVD) identifier?: Yes. CVE-2026-45364 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-33073.
When was CVE-2026-45364 published?: CVE-2026-45364 was published on 2026-05-28 and last updated on 2026-06-17.

References

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