CVE-2026-54688
MEDIUMCVE-2026-54688 is a medium-severity (CVSS 6.5) vulnerability in mcp-searxng. O3 Security confirms whether CVE-2026-54688 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
SearXNG MCP Server is Vulnerable to SSRF in web_url_read: the internal-address guard is disabled by default (MCP_HTTP_HARDEN off)
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
mcp-searxngnpmDescription
Ref: https://github.com/ihor-sokoliuk/mcp-searxng/issues/87#issuecomment-4645453694
Summary
The web_url_read tool fetches a caller-supplied URL server-side and converts it to markdown. An SSRF guard (assertUrlAllowed, which blocks private/loopback/metadata addresses) exists but runs only when MCP_HTTP_HARDEN=true, which is off by default. So in the default configuration there is no internal-address filtering, and an attacker who can influence the URL can make the server fetch internal services and cloud metadata and return their content. Confirmed on 1.1.0 (default config): web_url_read fetched a local internal sentinel and returned its content.
Details
dist/index.js (around lines 90-101): web_url_read calls fetchAndConvertToMarkdown on the caller URL. dist/url-reader.js (around lines 44-52): assertUrlAllowed performs the private-IP/loopback check, but only when the hardening flag is set; dist/http-security.js (around line 11) defaults MCP_HTTP_HARDEN to off. With the default config the check is skipped entirely. Even when enabled, the check is literal-hostname based with no DNS-rebinding or redirect re-check (the fetch follows redirects). file:// is rejected, so this is HTTP/HTTPS SSRF.
PoC
Re-validated on mcp-searxng 1.1.0 over MCP stdio in the default configuration (MCP_HTTP_HARDEN not set):
tools: searxng_web_search, web_url_read
web_url_read({ url: "http://127.0.0.1:<port>/internal" }) -> server fetched the internal sentinel; SSRF: CONFIRMED
The server fetched the loopback sentinel and returned its content. With MCP_HTTP_HARDEN=true the same request is blocked (policy error), confirming the guard exists but ships off. The same reaches http://169.254.169.254/... on cloud hosts.
Impact
In the default configuration an attacker who can influence the URL (LLM-produced and steerable via prompt injection) can make the server fetch internal-only HTTP services and the cloud metadata endpoint, returning their contents into the model context for exfiltration. The protection that would prevent it is not enabled by default.
Remediation
Enable the internal-address filtering by default (fail safe): make assertUrlAllowed run unconditionally and require an explicit opt-out only for trusted environments. Strengthen the check to resolve the host and reject loopback, link-local/metadata (169.254.0.0/16), 0.0.0.0/8, and private ranges, and re-validate on every redirect hop (or pin to the validated IP).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | mcp-searxng | all versions | 1.2.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mcp-searxng. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update mcp-searxng to 1.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54688 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-54688 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-54688. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54688 in your dependencies?
O3 detects CVE-2026-54688 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.