CVE-2026-45364Network attack vector

Rate-limit bypass via noncanonical IPv6 keys

Published May 28, 2026 · Updated May 28, 2026

Rate-limit bypass in Better Auth before 1.4.17 and 1.5.0-beta.1 through 1.5.0-beta.8 allows remote attackers to evade request limits. The getIp function returns the IP header's text unchanged, and onRequestRateLimit concatenates it with the path, so IPv6 aliases and rotated /64 addresses create distinct counter keys. Reachability requires IPv6 or an IPv6-form header and enabled rate limiting; exploitation permits unbounded authentication attempts but does not directly compromise accounts.

CVSS severity7.3
High
EPSS probability0.29%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Rate-limit bypass in Better Auth before 1.4.17 and 1.5.0-beta.1 through 1.5.0-beta.8 allows remote attackers to evade request limits. The getIp function returns the IP header's text unchanged, and onRequestRateLimit concatenates it with the path, so IPv6 aliases and rotated /64 addresses create distinct counter keys. Reachability requires IPv6 or an IPv6-form header and enabled rate limiting; exploitation permits unbounded authentication attempts but does not directly compromise accounts.

The record

CVE
CVE-2026-45364
Published
May 28, 2026
Updated
May 28, 2026
Vendor
Better Auth
Product
Better Auth
Classifications
CWE-307, CAPEC-49, CAPEC-600, T1110
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 28, 2026CVE publishedPublication date reported by the CVE source.
  2. May 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.4.17
  2. Affected versionversion=>= 1.5.0-beta.1, < 1.5.0-beta.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Better Auth · Better Authversion=< 1.4.17; version=>= 1.5.0-beta.1, < 1.5.0-beta.9

Published CVSS scores

7.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-307Improper Restriction of Excessive Authentication Attempts
CAPEC-49Password Brute Forcing
CAPEC-600Credential Stuffing
T1110Brute Force

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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