GHSA-5WF4-JQXH-8GM3

Vulnerability from github – Published: 2026-09-22 20:36 – Updated: 2026-09-22 20:36
VLAI
Summary
mcp-atlassian has an incomplete SSRF remediation
Details

Summary

The UserTokenMiddleware extracts URLs from X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url HTTP headers and passes them directly to API client constructors without any SSRF validation.

Affected Package

  • Ecosystem: PyPI
  • Package: mcp-atlassian
  • Affected versions: all versions before fix commit 5cd697dfce91
  • Patched versions: >= commit 5cd697dfce91

Details

In main.py, _process_authentication_headers() extracts URLs from ASGI headers without validation. In dependencies.py, get_jira_fetcher() creates JiraConfig with url=jira_url_header directly. There is no validate_url call, no IP range check, no hostname validation.

The fix adds URL validation to some paths but the header-based URL extraction in _process_authentication_headers() still passes raw URLs through. The derived config objects use the header URL directly and the fetcher makes HTTP requests to that URL.

PoC

jira_url_header = headers.get(b"x-atlassian-jira-url")
jira_url_str = jira_url_header.decode("latin-1") if jira_url_header else None
service_headers["X-Atlassian-Jira-Url"] = jira_url_str

Steps to reproduce: 1. git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test 2. cd /tmp/mcp-atlassian_test && git checkout 5cd697dfce91~1 3. pip install -e . 4. python3 poc.py

Expected output:

VULNERABILITY CONFIRMED
User-supplied URLs from HTTP headers passed directly to JiraConfig/JiraFetcher with no SSRF validation

Impact

An attacker can set X-Atlassian-Jira-Url: http://169.254.169.254/latest/meta-data/ to access AWS instance metadata, or target any internal service. The server makes authenticated HTTP requests to the attacker-specified URL.

Suggested Remediation

Validate all user-supplied URLs against an allowlist of permitted hostnames or reject private/loopback/link-local IP ranges. Consider requiring server-side configuration of allowed Atlassian instance URLs.

Severity
8.3 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mcp-atlassian"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.22.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-77267"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-22T20:36:17Z",
    "nvd_published_at": "2026-09-22T18:17:18Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe `UserTokenMiddleware` extracts URLs from `X-Atlassian-Jira-Url` and `X-Atlassian-Confluence-Url` HTTP headers and passes them directly to API client constructors without any SSRF validation.\n\n### Affected Package\n\n- **Ecosystem:** PyPI\n- **Package:** mcp-atlassian\n- **Affected versions:** all versions before fix commit 5cd697dfce91\n- **Patched versions:** \u003e= commit 5cd697dfce91\n\n### Details\n\nIn `main.py`, `_process_authentication_headers()` extracts URLs from ASGI headers without validation. In `dependencies.py`, `get_jira_fetcher()` creates `JiraConfig` with `url=jira_url_header` directly. There is no `validate_url` call, no IP range check, no hostname validation.\n\nThe fix adds URL validation to some paths but the header-based URL extraction in `_process_authentication_headers()` still passes raw URLs through. The derived config objects use the header URL directly and the fetcher makes HTTP requests to that URL.\n\n### PoC\n\n```python\njira_url_header = headers.get(b\"x-atlassian-jira-url\")\njira_url_str = jira_url_header.decode(\"latin-1\") if jira_url_header else None\nservice_headers[\"X-Atlassian-Jira-Url\"] = jira_url_str\n```\n\n**Steps to reproduce:**\n1. `git clone https://github.com/sooperset/mcp-atlassian /tmp/mcp-atlassian_test`\n2. `cd /tmp/mcp-atlassian_test \u0026\u0026 git checkout 5cd697dfce91~1`\n3. `pip install -e .`\n4. `python3 poc.py`\n\n**Expected output:**\n```\nVULNERABILITY CONFIRMED\nUser-supplied URLs from HTTP headers passed directly to JiraConfig/JiraFetcher with no SSRF validation\n```\n\n### Impact\n\nAn attacker can set `X-Atlassian-Jira-Url: http://169.254.169.254/latest/meta-data/` to access AWS instance metadata, or target any internal service. The server makes authenticated HTTP requests to the attacker-specified URL.\n\n### Suggested Remediation\n\nValidate all user-supplied URLs against an allowlist of permitted hostnames or reject private/loopback/link-local IP ranges. Consider requiring server-side configuration of allowed Atlassian instance URLs.",
  "id": "GHSA-5wf4-jqxh-8gm3",
  "modified": "2026-09-22T20:36:17Z",
  "published": "2026-09-22T20:36:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-5wf4-jqxh-8gm3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-77267"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/pull/1448"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sooperset/mcp-atlassian"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "mcp-atlassian has an incomplete SSRF remediation"
}



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