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CVE-2026-77267 medium CVSS 6.5

SSRF (Server-Side Request Forgery) in mcp-atlassian (CVE-2026-77267)

Summary

SSRF in mcp-atlassian (CVE-2026-77267). Confidential information can be exposed externally. Exploitable via UserTokenMiddleware. Mitigation: upgrade to 0.22.0 or later.

Original description

The description as published by the source.

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 wit…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-77267 has been found in mcp-atlassian.
Attackers can target a specific entry point like UserTokenMiddleware over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 6.5/10.
What to do: upgrade mcp-atlassian to 0.22.0 or later.
If unsure, ask your IT team or search "mcp-atlassian CVE-2026-77267" on the vendor's site.

CVE-2026-77267 (mcp-atlassian) — CWE-918 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: UserTokenMiddleware / main.py / dependencies.py / JiraConfig
Patched: 0.22.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

SSRF (CWE-918) exists in mcp-atlassian. Attackers reach the vulnerable code path via UserTokenMiddleware.

📍 Affected scope

Check the vendor advisory for the affected versions of mcp-atlassian. Attack surface: UserTokenMiddleware / main.py / dependencies.py / JiraConfig.

🔥 Severity

Severity: Medium (CVSS 6.5/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 0.22.0.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'mcp-atlassian' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'mcp-atlassian' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で mcp-atlassian を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade mcp-atlassian to 0.22.0

    ステージング環境で 0.22.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  3. 3
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

pip mcp-atlassian
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.22.0"}]}]

References

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