{"id":"CVE-2026-54688","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-54688","summary":"SearXNG MCP Server is Vulnerable to SSRF in web_url_read: the internal-address guard is disabled by default (MCP_HTTP_HARDEN off)","details":"Ref: https://github.com/ihor-sokoliuk/mcp-searxng/issues/87#issuecomment-4645453694\n\n\n### Summary\nThe 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.\n\n### Details\ndist/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.\n\n### PoC\nRe-validated on mcp-searxng 1.1.0 over MCP stdio in the default configuration (MCP_HTTP_HARDEN not set):\n```\ntools: searxng_web_search, web_url_read\nweb_url_read({ url: \"http://127.0.0.1:<port>/internal\" }) -> server fetched the internal sentinel; SSRF: CONFIRMED\n```\nThe 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.\n\n### Impact\nIn 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.\n\n### Remediation\nEnable 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).","published":"2026-08-19T19:23:08Z","modified":"2026-08-19T19:30:06.646108970Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[{"ecosystem":"npm","name":"mcp-searxng","fixedVersion":"1.2.1"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/ihor-sokoliuk/mcp-searxng/security/advisories/GHSA-q87f-qc2r-2gw4"},{"type":"WEB","url":"https://github.com/ihor-sokoliuk/mcp-searxng/issues/87#issuecomment-4645453694"},{"type":"PACKAGE","url":"https://github.com/ihor-sokoliuk/mcp-searxng"},{"type":"WEB","url":"https://github.com/ihor-sokoliuk/mcp-searxng/releases/tag/v1.2.1"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-19T19:30:06.646108970Z"}}