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.
Summary fetchToken in the OAuth2 SDK makes a POST to a builder-supplied URL with plain node-fetch, skipping the blacklist.isBlacklisted check that every other outbound fetch path in the codebase uses. The Joi schema for the OAuth2 URL has no scheme or host restriction. Alice, a builder, points an OAuth2 config at http://169.254.169.254/... or http://127.0.0.1:5984/; the server connects and returns response-body fragments in the validation result. Details packages/server/src/sdk/workspace/oauth2/utils.ts:17-65 defines fetchToken. Near the end: config.url is whatever the builder stored. fetchConfig has redirect: "follow" (the default), so a public URL that returns 302 to an internal target is also reachable. The route validation at packages/server/src/api/routes/oauth2.ts:9 accepts any string: The controller passes the URL into fetchToken through crud.ts. The /api/oauth2/validate endpoint (builder role) is the most direct attack path: it lives on builderRoutes, takes the URL from the body, fires the fetch, and returns a validation envelope that includes the upstream error string. Compare with every other outbound fetch in the codebase: packages/server/src/integrations/rest.ts:754 calls blacklist.isBlacklisted(url) before its fetch (though it does not re-check redirects; see companion advisory for REST-redirect SSRF). packages/backend-core/src/utils/outboundFetch.ts:98-100 sets redirect: "manual" and re-validates each hop. packages/server/src/automations/steps/outgoingWebhook.ts routes through fetchWithBlacklist. The default blacklist blocks 127.0.0.0/8, 169.254.0.0/16, 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16 (packages/backend-core/src/blacklist/blacklist.ts:6-16). The OAuth2 path never consults it. Proof of Concept Tested against Budibase 3.35.8 (built from master at f960e361). Step 1: Alice, a builder, POSTs an OAuth2 config pointed at CouchDB on the same host as Budibase: Server response: Budibase reached CouchDB (which rejects POST at / with 405). Without the blacklist bypass this request would be blocked at the IP check. Step 2: Probe the cloud metadata range: Server response: The "Not Found" substring is the upstream body; the server reached the link-local metadata endpoint and leaked the first bytes of the response into the validation error. Impact Two concrete paths, both reachable from any builder account (free-tier signup on Budibase Cloud is enough): 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/alldbs 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. 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. Recommended Fix Call blacklist.isBlacklisted before the fetch and set redirect: "manual" on fetchConfig, matching the pattern in outboundFetch.ts: Alternatively, replace the fetch call with fetchWithBlacklist, which handles both checks and re-validates redirect targets. Found by aisafe.io
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.
npm
@budibase/server (< 3.39.0)@budibase/server → 3.39.0 (npm)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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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.
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.
@budibase/server (npm) versions < 3.39.0 is affected.
Yes. CVE-2026-48153 is fixed in 3.39.0. Upgrade to this version or later.
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
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.
Upgrade @budibase/server to 3.39.0 or later.