SearXNG MCP Server: Unbounded Response Body Read Bypasses URL Size Limit in web_url_read

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2026-58483: 0.67% estimated exploitation activity in the next 30 days; percentile 52.03 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Unbounded Response Body Read Bypasses URL Size Limit in weburlread Summary The weburlread MCP tool in mcp-searxng enforces its 5 MiB response-size limit exclusively by inspecting the Content-Length header of a preliminary HEAD request. When a server omits Content-Length — a standard HTTP practice — checkContentLength() returns null, the guard condition short-circuits to false, and response.text() loads the entire response body into memory without any byte cap. An unauthenticated attacker who controls or can redirect to an HTTP endpoint can force the server process to consume unbounded memory and CPU, leading to a Denial of Service. Details weburlread is the entry point (src/index.ts:226-240). It passes the caller-supplied URL directly into readUrlContent() in src/url-reader.ts. Size-limit check (bypassed) checkContentLength() (src/url-reader.ts:243-245) returns null when the HEAD response carries no Content-Length header. Because the guard uses the !== null conjunction, a null result…

Published by the source

19 Jun 2026, 21:42 UTC

Last modified by the source

16 Sep 2026, 03:56 UTC

Source last checked

26 Oct 2026, 12:56 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xcqx-9jf5-w339

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xcqx-9jf5-w339

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# Patch Next advisory brief: CVE-2026-58483

Advisory: SearXNG MCP Server: Unbounded Response Body Read Bypasses URL Size Limit in `web_url_read`
IDs: CVE-2026-58483, GHSA-xcqx-9jf5-w339
Record: https://patchnext.com/advisories/cve-2026-58483 (revision 2, source checked 26 Oct 2026, 12:56 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-searxng 1.7.1. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm mcp-searxng: affected < 1.7.1; fixed in 1.7.1

## Suggested inspection (read-only)
- `npm ls mcp-searxng --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on mcp-searxng.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-xcqx-9jf5-w339 (OSV record GHSA-xcqx-9jf5-w339 lists affected ranges: npm mcp-searxng >=0 <1.7.1 (fixed))
- Verified: https://github.com/advisories/GHSA-xcqx-9jf5-w339 (GitHub-reviewed advisory GHSA-xcqx-9jf5-w339 lists affected ranges: npm mcp-searxng >=0 <1.7.1)

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