What is CVE-2026-121802?

CVE-2026-121802 is a critical-severity vulnerability in Better-Auth Better Auth, classified under Origin Validation Error. CVSS score: 9.1/10. Published 2026-11-04.

How severe is CVE-2026-121802?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Better-Auth Better Auth

CVE-2026-121802

@better-auth/expo before 1.7.16 allows certain account-takeover outcomes (e.g., unauthenticated changes of any account's email address), because it signs a caller-supplied state value without checking whether that value had been issued by the server. NOTE: the application secret must be rotated after updating to a fixed version.

Published 2026-11-04 · last modified 2026-11-04.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Better-Auth Better Auth

Weakness classification (CWE)

CWE-346 — Origin Validation Error

References

Frequently asked questions

What is CVE-2026-121802?: CVE-2026-121802 is a critical-severity vulnerability in Better-Auth Better Auth, classified under Origin Validation Error. CVSS score: 9.1/10. Published 2026-11-04.
How severe is CVE-2026-121802?: Critical severity. CVSS v3 base score is 9.1 out of 10.