CVE-2026-45061

Budibase is an open-source low-code platform. Prior to 3.35.10, the Plugin URL upload endpoint (POST /api/plugin) validates the submitted URL with a single substring check: url.includes(".tar.gz"). Any URL containing .tar.gz anywhere in the string — in the path, query string, or fragment — passes this check. The URL then proceeds directly to fetchWithBlacklist() with no further validation of host, scheme, or path. Standalone, this vulnerability is blocked by Budibase's default SSRF blacklist, which covers private IP ranges. But the URL validation layer itself is broken regardless, and it directly enables SSRF in two realistic situations: (1) when chained with the BLACKLIST_IPS bypass ([001]), where the blacklist is empty; and (2) when the plugin server follows HTTP redirects from an external URL to an internal target (the default node-fetch behavior with redirect: 'follow'). This vulnerability is fixed in 3.35.10.

Budibase is an open-source low-code platform. Prior to 3.35.10, the Plugin URL upload endpoint (POST /api/plugin) validates the submitted URL with a single substring check: url.includes(".tar.gz"). Any URL containing .tar.gz anywhere in the string — in the path, query string, or fragment — passes this check. The URL then proceeds directly to fetchWithBlacklist() with no further validation of host, scheme, or path. Standalone, this vulnerability is blocked by Budibase's default SSRF blacklist, which covers private IP ranges. But the URL validation layer itself is broken regardless, and it directly enables SSRF in two realistic situations: (1) when chained with the BLACKLIST_IPS bypass ([001]), where the blacklist is empty; and (2) when the plugin server follows HTTP redirects from an external URL to an internal target (the default node-fetch behavior with redirect: 'follow'). This vulnerability is fixed in 3.35.10.

1. Summary

| Field | Value | |-------|-------| | Title | SSRF via trivial .tar.gz substring bypass in Plugin URL upload | | Product | Budibase (Self-Hosted) | | Version | ≤ 3.34.11 (latest stable as of 2026-03-30) | | Component | packages/server/src/api/controllers/plugin/url.ts | | Vulnerability Type | CWE-918: Server-Side Request Forgery (SSRF), CWE-184: Incomplete List of Disallowed Inputs | | Severity | High (chained) / Medium (standalone) | | CVSS 3.1 Score (chained) | 7.7 — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N | | CVSS 3.1 Score (standalone) | 5.4 — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N | | Attack Vector | Network | | Privileges Required | Low (Global Builder role) | | User Interaction | None | | Affected Deployments | All Budibase instances with plugin loading enabled (default) |

2. Description

The Plugin URL upload endpoint (POST /api/plugin) validates the submitted URL with a single substring check: url.includes(".tar.gz"). Any URL containing .tar.gz anywhere in the string — in the path, query string, or fragment — passes this check. The URL then proceeds directly to fetchWithBlacklist() with no further validation of host, scheme, or path.

Standalone, this vulnerability is blocked by Budibase's default SSRF blacklist, which covers private IP ranges. But the URL validation layer itself is broken regardless, and it directly enables SSRF in two realistic situations: (1) when chained with the BLACKLIST_IPS bypass ([001]), where the blacklist is empty; and (2) when the plugin server follows HTTP redirects from an external URL to an internal target (the default node-fetch behavior with redirect: 'follow').

The developer team's own test suite (objectStore.spec.ts:393) tests that downloadTarballDirect passes through fetchWithBlacklist — confirming they're aware of the SSRF risk on this path. The .tar.gz substring check as the only URL-level guard was never intended to be the security boundary, but in practice it is.

3. Root Cause Analysis

3.1 Trivial substring-based URL validation

File: packages/server/src/api/controllers/plugin/url.ts

// Lines 7-19
export async function urlUpload(url: string, name = "", headers = {}) {
  if (!url.includes(".tar.gz")) {
    // ← ONLY validation: any URL with ".tar.gz" anywhere passes
    throw new Error("Plugin must be compressed into a gzipped tarball.")
  }

  const path = await downloadUnzipTarball(url, name, headers)
  // ↑ url is passed directly — no host allowlist, no scheme check, no path normalization
  try {
    return await getPluginMetadata(path)
  } catch (err) {
    deleteFolderFileSystem(path)
    throw err
  }
}

Problem: url.includes(".tar.gz") checks for a substring anywhere in the full URL string. It does not validate hostname, scheme, or that .tar.gz appears as an actual file extension at the end of the path.

3.2 Bypass examples

| Attack URL | includes(".tar.gz") | Actual request target | |------------|----------------------|----------------------| | http://169.254.169.254/.tar.gz | ✅ passes | AWS IMDS | | http://127.0.0.1:4005/_session.tar.gz | ✅ passes | CouchDB | | http://10.0.0.1:6379/.tar.gz | ✅ passes | Redis | | http://attacker.com/file.tar.gz?x=http://internal/ | ✅ passes | Redirect to internal | | http://internal-host/.tar.gz#fragment | ✅ passes | Internal service |

3.3 Developer awareness of SSRF risk on this path

File: packages/backend-core/src/objectStore/tests/objectStore.spec.ts

// Line 393
it("uses fetchWithBlacklist in downloadTarballDirect", async () => {
  downloadTarballDirect("http://169.254.169.254/metadata/v1/", "tmp")
  // ← team explicitly tests that IMDS is blocked via blacklist
})

The team knows this code path can reach IMDS. They rely on fetchWithBlacklist as the defense — but never tested the .tar.gz…

Budibase is an open-source low-code platform. Prior to 3.35.10, the Plugin URL upload endpoint (POST /api/plugin) validates the submitted URL with a single substring check: url.includes(".tar.gz"). Any URL containing .tar.gz anywhere in the string — in the path, query string, or fragment — passes this check. The URL then proceeds directly to fetchWithBlacklist() with no further validation of host, scheme, or path. Standalone, this vulnerability is blocked by Budibase's default SSRF blacklist, which covers private IP ranges. But the URL validation layer itself is broken regardless, and it directly enables SSRF in two realistic situations: (1) when chained with the BLACKLIST_IPS bypass ([001]), where the blacklist is empty; and (2) when the plugin server follows HTTP redirects from an external URL to an internal target (the default node-fetch behavior with redirect: 'follow'). This vulnerability is fixed in 3.35.10.

Budibase is an open-source low-code platform. Prior to 3.35.10, the Plugin URL upload endpoint (POST /api/plugin) validates the submitted URL with a single substring check: url.includes(".tar.gz"). Any URL containing .tar.gz anywhere in the string — in the path, query string, or fragment — passes this check. The URL then proceeds directly to fetchWithBlacklist() with no further validation of host, scheme, or path. Standalone, this vulnerability is blocked by Budibase's default SSRF blacklist, which covers private IP ranges. But the URL validation layer itself is broken regardless, and it directly enables SSRF in two realistic situations: (1) when chained with the BLACKLIST_IPS bypass ([001]), where the blacklist is empty; and (2) when the plugin server follows HTTP redirects from an external URL to an internal target (the default node-fetch behavior with redirect: 'follow'). This vulnerability is fixed in 3.35.10.

1. Summary

| Field | Value | |-------|-------| | Title | SSRF via trivial .tar.gz substring bypass in Plugin URL upload | | Product | Budibase (Self-Hosted) | | Version | ≤ 3.34.11 (latest stable as of 2026-03-30) | | Component | packages/server/src/api/controllers/plugin/url.ts | | Vulnerability Type | CWE-918: Server-Side Request Forgery (SSRF), CWE-184: Incomplete List of Disallowed Inputs | | Severity | High (chained) / Medium (standalone) | | CVSS 3.1 Score (chained) | 7.7 — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N | | CVSS 3.1 Score (standalone) | 5.4 — CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N | | Attack Vector | Network | | Privileges Required | Low (Global Builder role) | | User Interaction | None | | Affected Deployments | All Budibase instances with plugin loading enabled (default) |

2. Description

The Plugin URL upload endpoint (POST /api/plugin) validates the submitted URL with a single substring check: url.includes(".tar.gz"). Any URL containing .tar.gz anywhere in the string — in the path, query string, or fragment — passes this check. The URL then proceeds directly to fetchWithBlacklist() with no further validation of host, scheme, or path.

Standalone, this vulnerability is blocked by Budibase's default SSRF blacklist, which covers private IP ranges. But the URL validation layer itself is broken regardless, and it directly enables SSRF in two realistic situations: (1) when chained with the BLACKLIST_IPS bypass ([001]), where the blacklist is empty; and (2) when the plugin server follows HTTP redirects from an external URL to an internal target (the default node-fetch behavior with redirect: 'follow').

The developer team's own test suite (objectStore.spec.ts:393) tests that downloadTarballDirect passes through fetchWithBlacklist — confirming they're aware of the SSRF risk on this path. The .tar.gz substring check as the only URL-level guard was never intended to be the security boundary, but in practice it is.

3. Root Cause Analysis

3.1 Trivial substring-based URL validation

File: packages/server/src/api/controllers/plugin/url.ts

// Lines 7-19
export async function urlUpload(url: string, name = "", headers = {}) {
  if (!url.includes(".tar.gz")) {
    // ← ONLY validation: any URL with ".tar.gz" anywhere passes
    throw new Error("Plugin must be compressed into a gzipped tarball.")
  }

  const path = await downloadUnzipTarball(url, name, headers)
  // ↑ url is passed directly — no host allowlist, no scheme check, no path normalization
  try {
    return await getPluginMetadata(path)
  } catch (err) {
    deleteFolderFileSystem(path)
    throw err
  }
}

Problem: url.includes(".tar.gz") checks for a substring anywhere in the full URL string. It does not validate hostname, scheme, or that .tar.gz appears as an actual file extension at the end of the path.

3.2 Bypass examples

| Attack URL | includes(".tar.gz") | Actual request target | |------------|----------------------|----------------------| | http://169.254.169.254/.tar.gz | ✅ passes | AWS IMDS | | http://127.0.0.1:4005/_session.tar.gz | ✅ passes | CouchDB | | http://10.0.0.1:6379/.tar.gz | ✅ passes | Redis | | http://attacker.com/file.tar.gz?x=http://internal/ | ✅ passes | Redirect to internal | | http://internal-host/.tar.gz#fragment | ✅ passes | Internal service |

3.3 Developer awareness of SSRF risk on this path

File: packages/backend-core/src/objectStore/tests/objectStore.spec.ts

// Line 393
it("uses fetchWithBlacklist in downloadTarballDirect", async () => {
  downloadTarballDirect("http://169.254.169.254/metadata/v1/", "tmp")
  // ← team explicitly tests that IMDS is blocked via blacklist
})

The team knows this code path can reach IMDS. They rely on fetchWithBlacklist as the defense — but never tested the .tar.gz…