CVE-2026-4171
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 · uneditedA security vulnerability has been detected in CodeGenieApp serverless-express up to 4.17.1. Affected by this issue is some unknown functionality of the file examples/lambda-function-url/packages/api/models/TodoList.ts of the component API Endpoint. The manipulation of the argument userId leads to authorization bypass. The attack is possible to be carried out remotely. The exploit has been disclosed publicly and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
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 · moderate confidenceAuthorization bypass vulnerability in CodeGenieApp serverless-express API endpoint (up to v4.17.1). The vulnerability exists in the TodoList API model where manipulation of the userId argument allows attackers to bypass authorization controls, potentially accessing or modifying other users' data.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
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.
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Identify CodeGenieApp serverless-express installationLocate the serverless-express package in your project dependencies (package.json, requirements.txt, or installed packages). Run: npm list serverless-express OR pip list | grep serverless-expressAffected if The installed version is 4.17.1 or lower, or version cannot be determined (indicating unpatched older install)
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Verify TodoList API endpoint exposureReview your API routing configuration files for routes serving /todolist or /api/todos endpoints. Check if these endpoints accept userId as a query or body parameter.Affected if A TodoList API endpoint exists and accepts userId as an input parameter without server-side validation
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Inspect authorization logic for userId handlingExamine the server-side code handling the TodoList endpoint. Search for authorization checks that validate userId against the authenticated session. Look for patterns like: req.user.id === req.query.userId or similar session-to-parameter comparisons.Affected if No server-side validation exists that compares the provided userId against the authenticated user's identity from the session/token
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Test for authorization bypassWith an authenticated session for user A, make a request to the TodoList endpoint with userId parameter changed to user B's ID. Compare the response against a legitimate request for user A's data.Affected if The response contains data belonging to a different user than the authenticated session owner, confirming the authorization bypass
You are affected if serverless-express version 4.17.1 or lower is installed AND the TodoList API accepts userId parameter without validating it matches the authenticated user's session identity.
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.
From vendor dataUpgrade to a patched version beyond 4.17.1 when available; implement server-side validation of userId parameters against authenticated user session/context before granting access to resources.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
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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-2026-4171 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
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- Version or environment caveats, and links to real fixes
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