What is CVE-2026-109373?

CVE-2026-109373 is a high-severity vulnerability in Zitadel, classified under Unintended Proxy or Intermediary (Confused Deputy). CVSS score: 8.1/10. Published 2026-10-12.

How severe is CVE-2026-109373?

High severity. CVSS v3 base score is 8.1 out of 10.

Vulnerability in Zitadel

CVE-2026-109373

ZITADEL 3.0.0 before 4.19.2 contains an authentication bypass vulnerability in the Login V2 UI that allows unauthenticated attackers to obtain other users' session tokens by forging unsigned session cookies. Attackers can guess time-ordered session IDs around a victim's sign-in and supply them with empty tokens to receive rotated tokens, taking over accounts including MFA-completed administrator sessions.

Published 2026-10-12 · last modified 2026-10-12.

CVSS v3 metric

CVSS v3 base score 8.1 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

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

Zitadel

Weakness classification (CWE)

CWE-441 — Unintended Proxy or Intermediary (Confused Deputy)

References

github.com/zitadel/zitadel/security/advisories/GHSA-jh92-5mrj-p2w2 (vendor-advisory)
www.vulncheck.com/advisories/zitadel-3.0.0-before-4.19.2-account-takeover-via-u… (third-party-advisory)

Frequently asked questions

What is CVE-2026-109373?: CVE-2026-109373 is a high-severity vulnerability in Zitadel, classified under Unintended Proxy or Intermediary (Confused Deputy). CVSS score: 8.1/10. Published 2026-10-12.
How severe is CVE-2026-109373?: High severity. CVSS v3 base score is 8.1 out of 10.