high CVSS 7.7

CVE-2026-46555·Docker vulnerability

WhatsApp MCP Server is a Model Context Protocol (MCP) server for WhatsApp, enabling Claude to read and send WhatsApp messages. Prior to version 0.2.1, the `whatsapp-bridge` HTTP API listens on `127.0.0.1:8080` without authentication and without Host header validation, and the `/api/send` endpoint accepts an absolute `media_path` parameter without confining it to a safe directory. Combined, these issues allow any local process running as the same user as the bridge to send WhatsApp messages from the paired account without authorization; the same caller to read arbitrary files readable by the user (e.g. SSH private keys, browser session data, source code, dotfiles) and exfiltrate them as WhatsApp document attachments; and/or a remote attacker to trigger the same operations via DNS rebinding from a webpage the user visits, since no Host header validation is performed. In MCP environments, "local caller" extends beyond processes the user explicitly launched — sibling MCP servers, IDE extensions, and tool-triggered flows running in the user's session can act as the effective caller. This issue is fixed in whatsapp-mcp v0.2.1 and corresponding Docker images / release artifacts. Users should upgrade immediately. The fix introduces bearer token authentication on the bridge HTTP API (configured via environment variable, required on all requests, validated with constant-time comparison); host header allow-list validation to prevent DNS rebinding; and confinement of `media_path` to a configured directory, with rejection of absolute paths outside the root and path traversal sequences. This is a breaking change for clients of the bridge API. For users who cannot immediately upgrade: Stop the bridge, or block loopback access to port 8080, when the bridge is not actively in use; avoid running the bridge alongside untrusted MCP servers, browser extensions, or other untrusted local processes; avoid browsing untrusted sites while the bridge is running (DNS rebinding mitigation); and/or run the bridge under a dedicated user account or in a sandbox/container with no access to sensitive files.

Severity
high
Software
Docker
Fixed in
0.2.1
Published
2026-07-20

Affected versions

Until: 0.2.1

Fixed in: 0.2.1

How to fix this CVE

Upgrade WhatsApp MCP Server to version 0.2.1 or later immediately. This version introduces bearer token authentication, Host header validation, and confines file access to safe directories. If immediate upgrade is not possible, disable the bridge when not in use or block loopback access to port 8080.

sudo dnf update docker-ce

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

POST /api/send HTTP/1.1
Host: 127.0.0.1:8080
.*media_path.*(/etc/passwd|/root/\.ssh|/home.*\.ssh)

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement Host header validation to reject requests not matching the allowlist; require Bearer token authentication on all /api/send endpoints; validate and canonicalize the media_path parameter to reject absolute paths and path traversal sequences (../, ..\ patterns); restrict file access to a designated safe directory.

How to check if you are affected

  1. Check installed Docker version: docker --version
  2. Verify if WhatsApp MCP Server is running: docker ps | grep whatsapp
  3. If running, check the image tag: docker inspect <container_id> | grep -i image
  4. Test for unauthenticated API access: curl -X GET http://127.0.0.1:8080/api/status (should fail or require auth in v0.2.1+)
  5. Review container logs for suspicious /api/send requests without authentication: docker logs <container_id> | grep -i '/api/send'
  6. Confirm fix applied: docker images | grep whatsapp and verify tag is v0.2.1 or later

FAQ

What is CVE-2026-46555?

This vulnerability affects WhatsApp MCP Server versions prior to 0.2.1, where the HTTP bridge API listens without authentication and performs insufficient validation on file paths, allowing unauthorized message sending and sensitive file exfiltration by local processes or remote attackers via DNS rebinding.

Is CVE-2026-46555 being actively exploited?

No, CVE-2026-46555 is not currently listed in CISA's Known Exploited Vulnerabilities catalog and no public exploit code is available.

What versions of WhatsApp MCP Server are affected by CVE-2026-46555?

All versions prior to 0.2.1 are vulnerable; version 0.2.1 and later contain the security fix.

How do I check if my server is vulnerable to CVE-2026-46555?

Run `docker images | grep whatsapp` and verify the tag; if it shows a version earlier than v0.2.1, the system is vulnerable. Additionally, test for unauthenticated API access on localhost:8080.

Does Defensia detect CVE-2026-46555?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker with WhatsApp MCP Server is deployed on a monitored server, CVE-2026-46555 will appear in your dashboard with remediation steps.

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References

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