CVE-2026-27840Network attack vector

Invalid-token acceptance via unchecked OIDC subject

Published Feb 26, 2026 · Updated Feb 26, 2026

Authentication bypass in affected ZITADEL versions allows remote attackers to submit truncated v2 opaque OIDC access tokens that remain valid. TokenVerifierRepo verifies v2 tokens from database-backed session identifiers but formerly ignored the decrypted subject instead of comparing it with the stored user ID. Reproduction requires a legitimate v2 token and user interaction; the vendor considers the behavior nonexploitable and reports no cross-user access.

CVSS severity4.3
Medium
EPSS probability0.14%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in affected ZITADEL versions allows remote attackers to submit truncated v2 opaque OIDC access tokens that remain valid. TokenVerifierRepo verifies v2 tokens from database-backed session identifiers but formerly ignored the decrypted subject instead of comparing it with the stored user ID. Reproduction requires a legitimate v2 token and user interaction; the vendor considers the behavior nonexploitable and reports no cross-user access.

The record

CVE
CVE-2026-27840
Published
Feb 26, 2026
Updated
Feb 26, 2026
Vendor
ZITADEL
Product
ZITADEL
Classifications
CWE-302
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 26, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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

  1. Affected versionversion=>= 2.31.0, <= 2.71.19
  2. Affected versionversion=>= 3.0.0, < 3.4.7
  3. Affected versionversion=>= 4.0.0, < 4.11.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

ZITADEL · ZITADELversion=>= 2.31.0, <= 2.71.19; version=>= 3.0.0, < 3.4.7; version=>= 4.0.0, < 4.11.0

Published CVSS scores

4.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

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-302Authentication Bypass by Assumed-Immutable Data

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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