CVE-2026-40165Network attack vector

Account takeover via SAML NameID truncation

Published May 20, 2026 · Updated May 20, 2026

Authentication bypass in authentik before 2025.12.5 and 2026.2.0-rc1 through 2026.2.2 allows remote authenticated users to access other accounts. The SAML response processor read only the NameID element's text before an embedded XML comment, so account lookup used a truncated identifier. Exploitation requires a SAML Source account whose NameID can be changed and an instance with XML Signing enabled; success grants access to any user account.

CVSS severity8.7
High
EPSS probability0.50%
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 authentik before 2025.12.5 and 2026.2.0-rc1 through 2026.2.2 allows remote authenticated users to access other accounts. The SAML response processor read only the NameID element's text before an embedded XML comment, so account lookup used a truncated identifier. Exploitation requires a SAML Source account whose NameID can be changed and an instance with XML Signing enabled; success grants access to any user account.

The record

CVE
CVE-2026-40165
Published
May 20, 2026
Updated
May 20, 2026
Vendor
Authentik Security Inc.
Product
authentik
Classifications
CWE-287, CWE-91, CWE-436, T1078
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 20, 2026CVE publishedPublication date reported by the CVE source.
  2. May 20, 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=< 2025.12.5
  2. Affected versionversion=>= 2026.2.0-rc1, < 2026.2.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Authentik Security Inc. · authentikversion=< 2025.12.5; version=>= 2026.2.0-rc1, < 2026.2.3

Published CVSS scores

8.7GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/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
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-91XML Injection (aka Blind XPath Injection)
CWE-436Interpretation Conflict
T1078Valid Accounts

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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