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CWE-290Weakness · CWE-290

CVE-2026-55641

HIGH · 8.2 CVSS v3.1 Published 2026-07-10
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
91/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
9Router is an AI router & token saver. Prior to 0.5.2, 9router determines whether a /v1 LLM proxy request is local by reading the client-controlled Host header, allowing a remote unauthenticated attacker to send Host: localhost and bypass API-key authentication. In the default configuration, this exposes the /v1 proxy to upstream provider calls using stored provider credentials and allows /v1/search with the searxng provider_options.baseUrl parameter to drive server-side requests to internal or cloud-metadata hosts. This issue is fixed in version 0.5.2.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

9Router versions before 0.5.2 use the client-supplied Host HTTP header to determine whether a /v1 LLM proxy request is local, allowing unauthenticated attackers to bypass API-key authentication by sending 'Host: localhost'. This exposes the /v1 proxy to upstream provider calls using stored credentials and enables SSRF via /v1/search with searxng's provider_options.baseUrl parameter to target internal or cloud-metadata endpoints.

MitigationUpgrade to version 0.5.2 or later, which implements proper Host header validation and no longer relies on client-controlled headers for authentication decisions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify 9Router installation and version
    Locate the 9Router binary or package and run '9router --version' or check the installed package version (e.g., via package manager: 'npm list 9router' or 'pip show 9router')
    Affected if The installed version is before 0.5.2 (e.g., 0.5.1, 0.5.0, etc.)
  2. Verify /v1 proxy endpoint is exposed
    Send a request to the /v1 endpoint (e.g., curl -i http://TARGET:PORT/v1/models -H 'Host: localhost') without any authentication headers
    Affected if The /v1 endpoint responds without requiring API-key authentication when a 'Host: localhost' header is supplied
  3. Confirm Host header is used for local/remote routing
    Inspect the application configuration or logs when making requests with different Host headers; compare behavior between 'Host: localhost' and 'Host: actual hostname'
    Affected if Requests with 'Host: localhost' bypass authentication while the same request with a different Host header requires authentication, indicating the vulnerability is present
  4. Check for stored provider credentials
    Review 9Router configuration files (e.g., config.yaml, .env, or similar) for stored API keys or credentials for upstream LLM providers
    Affected if Credentials for upstream providers (OpenAI, Anthropic, etc.) are configured and the /v1 proxy is exposed, enabling potential credential abuse

You are affected if 9Router version is below 0.5.2 AND the /v1 proxy endpoint is accessible with 'Host: localhost' bypassing API-key authentication, exposing stored provider credentials.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Upgrade to version 0.5.2 or later, which implements proper Host header validation and no longer relies on client-controlled headers for authentication decisions.

Recommended fix High confidence

0.5.2

  1. Identify the currently installed 9Router version by checking the application or its configuration files
  2. Plan for upgrade by reviewing the 9Router 0.5.2 release notes for any configuration or behavioral changes
  3. Backup the current 9Router configuration and any stored credentials
  4. Upgrade 9Router to version 0.5.2 using the appropriate installation method (e.g., package manager, binary replacement, or container update)
  5. After upgrading, verify that the Host header is no longer trusted for local/remote request determination
  6. Test that API-key authentication is now properly enforced for /v1 proxy requests regardless of Host header value
  7. Confirm that /v1/search with searxng provider_options.baseUrl is properly restricted and cannot be abused for SSRF
Caveat Review release notes for 0.5.2; while primarily a security fix, verify that any authentication or routing behavior changes do not impact existing integrations

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation3.0 h
  • Implementation2.0 h
  • Testing4.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,920
Get the patch applied

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,072.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-55641 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
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  • Version or environment caveats, and links to real fixes
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