How should we interpret CVSS severity scores?

CVSS estimates technical severity, but it does not automatically equal business risk. Prioritize using context like internet exposure, asset criticality, known exploitation, and whether compensating controls exist. A Medium CVSS on an exposed production system can be more urgent than a Critical on an isolated non-production host.

Vulnerability Database

Q: What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

Q: What's the difference between a vulnerability, an exploit, and a zero-day?

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. Risk increases sharply when exploitation becomes reliable or widespread.

Q: Why do vulnerabilities keep reappearing in our environment?

Recurring findings usually come from incomplete asset discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host.

Q: How do we prioritize remediation without burning out the team?

Use a repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress so remediation is steady, not reactive.

Q: How can SynScan help reduce vulnerability risk over time?

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.

352,262

Total vulnerabilities in the database

CVE-2026-54353 — @budibase / backend-core

Time-of-check Time-of-use (TOCTOU) Race Condition

Summary

Authenticated users with automation permissions can bypass Budibase's SSRF blacklist through DNS rebinding.

The outbound fetch flow validates a hostname against the blacklist before the request is sent, but the actual socket connection later performs a separate DNS lookup through node-fetch. Since the validated IPs are never pinned to the connection, an attacker-controlled hostname can return a public IP during validation and a private/internal IP during the real connection.

This results in a non-blind SSRF primitive against internal services reachable from the Budibase host, including loopback, RFC1918 ranges, and cloud metadata endpoints.

Details

The issue comes from the outbound fetch validation flow resolving DNS twice:

During blacklist validation Again during the real socket connection

The first lookup result is discarded after validation, so the second lookup is free to resolve to a different IP.

This creates a classic TOCTOU DNS rebinding issue.

Affected flow in:

packages/backend-core/src/utils/outboundFetch.ts

async function throwIfUnsafe(url: string): Promise&lt;void&gt; {
  const parsed = parseUrl(url)

  if (await isBlacklisted(parsed.hostname)) {
    throw new Error(&quot;URL is blocked or could not be resolved safely.&quot;)
  }
}

for (let redirects = 0; redirects &lt;= MAX_REDIRECTS; redirects++) {
  await throwIfUnsafe(nextUrl)

  const response = await fetchFn(nextUrl, nextRequest)

  // ...
}

fetchFn uses plain node-fetch with no custom http.Agent / https.Agent, so the underlying socket performs its own independent dns.lookup after validation completes.

The same pattern also exists in:

packages/server/src/automations/steps/utils.ts

await throwIfBlacklisted(nextUrl)

const response = await fetch(nextUrl, nextRequest)

The blacklist implementation resolves hostnames but only returns a boolean:

packages/backend-core/src/blacklist/blacklist.ts

async function lookup(address: string): Promise&lt;string[]&gt; {
  address = parseAddress(address)

  const addresses = await performLookup(address, { all: true })

  return addresses.map(addr =&gt; addr.address)
}

export async function isBlacklisted(address: string): Promise&lt;boolean&gt; {
  // ...

  if (!net.isIP(address)) {
    try {
      ips = await lookup(address)
    } catch (e) {
      /* ... */
    }
  } else {
    ips = [address]
  }

  return ips.some(ip =&gt; blackList!.check(ip, getIpVersion(ip)))
}

The resolved IPs are discarded, so callers cannot pin the later socket connection to the validated addresses.

An attacker controlling authoritative DNS for a hostname can therefore return:

a public IP during validation a private/internal IP during the actual connection

Anything routing through these helpers inherits the issue, including:

outgoing webhook Slack Discord Make Zapier n8n AI extract object-store fetches

Several of these steps return upstream response content directly into automation output, which makes the SSRF non-blind.

PoC

Tested locally against a self-hosted build from master. No Budibase-operated infrastructure was touched.

Run Budibase locally.

Start a harmless local HTTP listener:

python3 -m http.server 8080 --bind 127.0.0.1

Use a rebinding hostname such as:

7f000001.cb007264.rbndr.us

which rotates between:

127.0.0.1 203.0.113.100

Steps to reproduce:

Log into Budibase with automation permissions. Create an automation using the Outgoing Webhook step. Set the URL to: http://<rebinding-host>:8080/ Trigger the automation.

Observed result:

The blacklist validation resolves the hostname to the public IP and allows the request. node-fetch performs a second DNS lookup during socket creation. The second lookup resolves to 127.0.0.1. The TCP connection lands on the local service. The local server response body appears directly in the automation output. Impact

This produces a non-blind read-SSRF primitive against anything reachable from the Budibase host process, including:

loopback services (127.0.0.1) RFC1918 ranges internal Kubernetes/VPC services cloud metadata endpoints (169.254.169.254)

On cloud deployments without IMDSv2 enforcement, this may expose temporary IAM credentials via:

/latest/meta-data/iam/security-credentials/<role>

On multi-tenant hosted deployments, this may also create potential cross-tenant access paths through shared internal infrastructure.

Published: Jun 22, 2026
Updated: Jun 23, 2026
CVE: CVE-2026-54353
GHSA: GHSA-gfq7-5x4g-3xhf
Severity: High
Exploit:
CISA KEV:

CVSS v3:

Severity: High
Score: 8.5
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N

CWEs:

Affected Software
References

Software	From	Fixed in
@budibase / backend-core	-	3.39.9

https://github.com/Budibase/budibase/security/advisories/GHSA-gfq7-5x4g-3xhf

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Frequently Asked Questions

What is a Vulnerability (CVE) and why does it matter?

A security vulnerability is a weakness in software, hardware, or configuration that can be exploited to compromise confidentiality, integrity, or availability. Many vulnerabilities are tracked as CVEs (Common Vulnerabilities and Exposures), which provide a standardized identifier so teams can coordinate patching, mitigation, and risk assessment across tools and vendors.

CVSS (Common Vulnerability Scoring System) estimates technical severity, but it doesn't automatically equal business risk. Prioritize using context like internet exposure, affected asset criticality, known exploitation (proof-of-concept or in-the-wild), and whether compensating controls exist. A "Medium" CVSS on an exposed, production system can be more urgent than a "Critical" on an isolated, non-production host.

A vulnerability is the underlying weakness. An exploit is the method or code used to take advantage of it. A zero-day is a vulnerability that is unknown to the vendor or has no publicly available fix when attackers begin using it. In practice, risk increases sharply when exploitation becomes reliable or widespread.

Recurring findings usually come from incomplete Asset Discovery, inconsistent patch management, inherited images, and configuration drift. In modern environments, you also need to watch the software supply chain: dependencies, containers, build pipelines, and third-party services can reintroduce the same weakness even after you patch a single host. Unknown or unmanaged assets (often called Shadow IT) are a common reason the same issues resurface.

Use a simple, repeatable triage model: focus first on externally exposed assets, high-value systems (identity, VPN, email, production), vulnerabilities with known exploits, and issues that enable remote code execution or privilege escalation. Then enforce patch SLAs and track progress using consistent metrics so remediation is steady, not reactive.

SynScan combines attack surface monitoring and continuous security auditing to keep your inventory current, flag high-impact vulnerabilities early, and help you turn raw findings into a practical remediation plan.