CVE-2026-62863: MoLing: unauthenticated SSE and wildcard CORS expose tool sessions

What it is

MoLing is a computer-use and browser-use based MCP server. Prior to 0.5.0, when MoLing runs in SSE mode using `-l`, its `/sse` and `/message` HTTP endpoints do not authenticate requests and the `mcp-go` dependency sets `Access-Control-Allow-Origin: *`. A malicious web page can open a cross-origin `EventSource` to `/sse`, including a loopback listener, and read the `endpoint` event to obtain `sessionId`. After a victim running SSE mode visits that page, the attacker can use the disclosed `sessionId` against `/message` to send unauthorized MCP tool calls. Depending on the configured tools, those calls can read or write local files, execute commands or perform other actions. Binding only to loopback does not prevent this browser-mediated attack. This issue is fixed in version 0.5.0.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-10-30).

Weakness: CWE-942: Permissive Cross-domain Policy with Untrusted Domains; CWE-306: Missing Authentication for Critical Function

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and a user must take an action. Impact: confidentiality high, integrity high, availability low. CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:L

CISA assessment (SSVC): CISA assesses that a public proof of concept exists. Automatable: no. Technical impact: total.

Public exploit evidence (Exploit Observer)

Exploit Observer found 5 code repositories naming this CVE.

Code repositories that name a CVE are often scanners, copies or fakes, and some are malware. Read the code before running anything.

See all 6 references on Exploit Observer

Live scores

EPSS

0.003
low predicted chance of attack

VEDAS

0.987
strong exploit evidence

On CISA KEV

Not listed

Detection rule

Nuclei · Suricata

Who is affected

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

How to fix it

No fixed version or vendor advisory is listed in the CVE record yet. Watch the vendor’s security page.

How to detect it

Nuclei template (active check)

MoLing - Unauthenticated MCP SSE Session Disclosure

MoLing is a computer-use and browser-use based MCP server. Prior to 0.5.0, when MoLing runs in SSE mode (`-l`), its `/sse` and `/message` HTTP endpoints do not authenticate requests and the `mcp-go` dependency sets `Access-Control-Allow-Origin: *`. An unauthenticated client can open an `EventSource` to `/sse` and read the `endpoint` event to obtain a `sessionId`, which can then be used against `/message` to send unauthorized MCP tool calls (local file read/write, command execution, etc.). This template connects unauthenticated to `/sse` and confirms a session id is disclosed. Fixed in 0.5.0.

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

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

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

nuclei -u https://your-host -t CVE-2026-62863.yaml

id: CVE-2026-62863

info:
  name: "MoLing - Unauthenticated MCP SSE Session Disclosure"
  author: vedas-arpsyndicate
  severity: high
  description: |
    MoLing is a computer-use and browser-use based MCP server. Prior to 0.5.0, when MoLing runs in
    SSE mode (`-l`), its `/sse` and `/message` HTTP endpoints do not authenticate requests and the
    `mcp-go` dependency sets `Access-Control-Allow-Origin: *`. An unauthenticated client can open an
    `EventSource` to `/sse` and read the `endpoint` event to obtain a `sessionId`, which can then be
    used against `/message` to send unauthorized MCP tool calls (local file read/write, command
    execution, etc.). This template connects unauthenticated to `/sse` and confirms a session id is
    disclosed. Fixed in 0.5.0.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-62863&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=moling&match=exact
  classification:
    cve-id: CVE-2026-62863
    cwe-id: CWE-306
  metadata:
    verified: false
    max-request: 1
  tags: cve,cve2026,moling,auth-bypass
http:
  - method: GET
    path:
      - "{{BaseURL}}/sse"
    matchers-condition: and
    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'contains(content_type, "text/event-stream")'
          - 'contains(body, "sessionId")'
        condition: and

CVE-2026-62863.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-62863 MoLing - Unauthenticated MCP SSE Session Disclosure. Add them to your Suricata rule set and reload.

alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-62863 MoLing - Unauthenticated MCP SSE Session Disclosure"; flow:established,to_server; http.method; content:"GET"; http.uri; content:"/sse"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-62863; reference:url,https://www.exploit.observer/?keyword=CVE-2026-62863&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=moling&match=exact; sid:1103004; rev:1;)

CVE-2026-62863.rules on GitHub

References

Other references

• https://github.com/gojue/moling/security/advisories/GHSA-qpgh-hp5g-4vwp (x_refsource_CONFIRM)
• https://github.com/gojue/moling/pull/48 (x_refsource_MISC)
• https://github.com/gojue/moling/commit/ae07f704cbc88d4419fc0fbaec278090fcd0502d (x_refsource_MISC)
• https://github.com/gojue/moling/releases/tag/v0.5.0 (x_refsource_MISC)

Other databases

• CVE record (cve.org)
• NVD
• Exploit Observer

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.