CVE-2026-40165
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedauthentik is an open-source identity provider. Versions 2025.12.4 and prior, and versions 2026.2.0-rc1 through 2026.2.2 were vulnerable to Authentication Bypass through SAML NameID XML Comment Injection. Due to how authentik extracted the NameID value from a SAML assertion, it was possible for an attacker to trick authentik into only seeing a part of the NameID value, potentially allowing an attacker to gain access to other accounts. This issue could be exploited on an authentik instance with a SAML Source, where the attacker had an account on the SAML Source and the ability to modify their NameID value (commonly username or E-mail), and XML Signing was enabled. The attacker could modify the SAML assertion given to authentik by injecting a comment within the NameID value, which effectively truncated the NameID value to the snippet before the comment, and gave the attacker access to any user account. This issue has been fixed in versions 2025.12.5 and 2026.2.3.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisA detailed technical summary for this CVE is being prepared.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2025.12.5 or 2026.2.3 (depending on your current branch)
- 1. Identify the current authentik version by checking the authentik admin interface or running 'helm list'/'docker ps' depending on your deployment method
- 2. If running version 2025.12.4 or earlier, upgrade to version 2025.12.5
- 3. If running version 2026.2.0-rc1 through 2026.2.2, upgrade to version 2026.2.3
- 4. After upgrade, verify the SAML Source configuration still works correctly by testing authentication
Generated from the published advisory — verify against the referenced sources before acting.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-40165 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-40165 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data