CVE-2026-81735: bytedance UI-TARS-desktop advisory

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

What it is

startServer.ts in the mcp-http-server package of UI-TARS-desktop defaulted its listen address to ‘::’ when no host was given, so startSseAndStreamableHttpMcpServer bound the Streamable HTTP and SSE MCP transports to every interface, and its authentication middleware was optional: middlewares are applied only when a caller supplies them. The @agent-infra/mcp-server-commands and @agent-infra/mcp-server-filesystem entry points call startSseAndStreamableHttpMcpServer with a host and port alone and pass no middleware, so neither server required a credential. The commands server exposes a run_command tool that hands its caller-supplied command string to promisify(child_process.exec), so any unauthenticated client able to reach the port could run arbitrary commands as the user running the server, and the filesystem server exposed its file read and write tools on the same terms. The listen default became 127.0.0.1 in commit c2ad42e3eb9b27830db41a3e6f51ca7179d9b168; the package version stayed at 1.2.4 across that change, so the boundary is the commit rather than a release.

Description quoted from the CVE record (assigned by VulnCheck, published 2026-08-27).

Weakness: Missing Authentication for Critical Function

How it can be exploited

Exploitable over the network with low attack complexity with no special attack requirements needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

CISA assessment (SSVC): CISA has no evidence of exploitation. Automatable: yes. Technical impact: total.

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-67078, GHSA-p68p-fq8j-3639

VEDAS cluster: VEDAS:DEFTDYNAMO

Exploit Observer links 5 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (5)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Vulnerability databases and vendor advisories (3)

Catalogue entries, not exploit evidence.

Vulnerability database or vendor advisory: https://euvd.enisa.europa.eu/enisa/EUVD-2026-67078
Vulnerability database or vendor advisory: https://github.com/advisories/GHSA-p68p-fq8j-3639
Vulnerability database or vendor advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-81735

2 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS: 0.008
low predicted chance of attack
VEDAS: 0.989
strong exploit evidence
On CISA KEV: Not listed
Detection rule: Nuclei · Suricata

Who is affected

Product	Affected	Not affected
bytedance UI-TARS-desktop	before c2ad42e3eb9b (git commit)	c2ad42e3eb9b is not affected

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

How to fix it

Vendor guidance:

Pull Request #1918 (issue-tracking, patch)
Patch Commit (patch)

How to detect it

Nuclei template (active check)

UI-TARS-desktop mcp-http-server - Unauthenticated MCP Command Execution Exposure
The mcp-http-server package of UI-TARS-desktop defaulted its listen address to ‘::’ and applied authentication middleware only when a caller supplied one. The @agent-infra/mcp-server-commands and @agent-infra/mcp-server-filesystem entry points start the Streamable HTTP / SSE MCP transports with no middleware, so any unauthenticated client able to reach the port can complete the MCP handshake and invoke the run_command tool, which passes a caller-supplied command to child_process.exec, yielding remote command execution. Fixed by defaulting the listen address to 127.0.0.1 in commit c2ad42e3.

Name and description quoted from the template, written by VEDAS.

The template sends 1 request (POST /mcp); it decides using dsl matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash

nuclei -u https://your-host -t CVE-2026-81735.yaml

Show the template (42 lines)

yaml

id: CVE-2026-81735

info:
  name: "UI-TARS-desktop mcp-http-server - Unauthenticated MCP Command Execution Exposure"
  author: vedas-arpsyndicate
  severity: critical
  description: |
    The mcp-http-server package of UI-TARS-desktop defaulted its listen address to '::' and
    applied authentication middleware only when a caller supplied one. The
    @agent-infra/mcp-server-commands and @agent-infra/mcp-server-filesystem entry points start
    the Streamable HTTP / SSE MCP transports with no middleware, so any unauthenticated client
    able to reach the port can complete the MCP handshake and invoke the run_command tool,
    which passes a caller-supplied command to child_process.exec, yielding remote command
    execution. Fixed by defaulting the listen address to 127.0.0.1 in commit c2ad42e3.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-81735&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=ui-tars&match=exact
  classification:
    cvss-metrics: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
    cvss-score: 10.0
    cve-id: CVE-2026-81735
    cwe-id: CWE-306
  metadata:
    verified: false
  tags: cve,cve2026,ui-tars,mcp,rce
http:
  - raw:
      - |
        POST /mcp HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/json
        Accept: application/json, text/event-stream

        {"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2025-06-18","capabilities":{},"clientInfo":{"name":"mcp","version":"1.0"}}}

    matchers:
      - type: dsl
        dsl:
          - 'contains(body, "protocolVersion")'
          - 'contains(body, "jsonrpc")'
          - 'status_code == 200'
        condition: and

CVE-2026-81735.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-81735 UI-TARS-desktop mcp-http-server - Unauthenticated MCP Handshake Attempt. Add them to your Suricata rule set and reload.

Show the rules

suricata

alert http $EXTERNAL_NET any -> $HOME_NET any (msg:"VEDAS CVE-2026-81735 UI-TARS-desktop mcp-http-server - Unauthenticated MCP Handshake Attempt"; flow:established,to_server; http.method; content:"POST"; http.uri; content:"/mcp"; nocase; http.request_body; content:"initialize"; nocase; fast_pattern; content:"jsonrpc"; nocase; classtype:attempted-admin; reference:cve,CVE-2026-81735; reference:url,https://www.exploit.observer/?keyword=CVE-2026-81735&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=ui-tars&match=exact; sid:1081401; rev:1;)

CVE-2026-81735.rules on GitHub

References

Vendor advisories and patches

Pull Request #1918 (issue-tracking, patch)
Patch Commit (patch)

Exploits and technical analysis

Other references

https://github.com/bytedance/UI-TARS-desktop (product)

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.