CVE-2026-42849
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. Prior to versions 2025.12.5 and 2026.2.3, due to the implementation of stages in the SFE (Simple Flow Executor) in order to make the interface more compatible with legacy browsers, it was possible to use an XSS exploit in the AutosubmitStage. This issue has been patched 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 analysis · high confidenceAn XSS vulnerability exists in the AutosubmitStage of the Simple Flow Executor (SFE) in authentik identity provider. The SFE implementation included measures for legacy browser compatibility that inadvertently allowed script injection via the AutosubmitStage, enabling attackers to execute malicious JavaScript in users' browsers.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 2025.12.5>= 2026.2.0, < 2026.2.3CVSS 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
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
-
Identify authentik installation and versionCheck the installed authentik version by examining the package manager, docker container labels, or the authentik admin interface under 'System' > 'Version'. In docker deployments, inspect the authentik container image tags or docker-compose.yml version. In bare-metal installations, check the pip package version with 'pip show authentik' or equivalent.Affected if The installed version is less than 2025.12.5, or greater than or equal to 2026.2.0 but less than 2026.2.3
-
Locate flows using the AutosubmitStageIn the authentik admin interface, navigate to 'Flows' and examine each flow's stages. Look for any flow that includes an AutosubmitStage in its stage list. Alternatively, query the authentik API endpoint /api/v1/flow/stages/ or inspect the underlying database tables for stage entries where the stage_type contains 'AutosubmitStage'.Affected if There exists a flow that includes an AutosubmitStage, making that flow potentially vulnerable to the stored XSS flaw
-
Verify the SFE component is in useThe vulnerability affects the Simple Flow Executor (SFE). Check if flows are configured to use SFE by default or explicitly. In the authentik UI, this is typically the default flow executor. No specific configuration file inspection is required as this is the standard execution path.Affected if Flows are executed using the default SFE (Simple Flow Executor), which is the standard configuration in authentik
A user is affected if their authentik version falls within the vulnerable ranges AND they have any flow configured with an AutosubmitStage that processes user-supplied input.
Generated from the published advisory. Verify against your own configuration.
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 · scoped2025.12.52026.2.3
Upgrade authentik to version 2025.12.5 or 2026.2.3 or later to patch the XSS vulnerability in the AutosubmitStage.
2025.12.5 or 2026.2.3 (upgrade to the latest stable version within your release branch)
- Determine your current Authentik version using your package manager or deployment method
- Upgrade to version 2025.12.5 or 2026.2.3 (whichever is compatible with your release branch)
- Verify the upgrade completed successfully
- Test that the AutosubmitStage functionality works as expected
- Confirm the XSS vulnerability is no longer present
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation3.0 h
- Implementation2.0 h
- Testing5.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,312.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-42849 — 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-2026-42849 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