SSRF (Server-Side Request Forgery) in mcp-atlassian (CVE-2026-27826)

Summary

SSRF in mcp-atlassian (CVE-2026-27826). Confidential information can be exposed externally. Exploitable via GET /rest/api/2/myself. Mitigation: upgrade to 0.17.0 or later.

Original description

The description as published by the source.

Summary

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.

Details

The server supports a multi-tenant HTTP authentication mode where clients supply per-request Jira/Confluence URLs via custom headers. The middleware (src/mcp_atlassian/servers/main.py:436–448) extracts X-Atlassian-Jira-Url from the request and stores it in request state with no validation. The dependency provider (src/mcp_atlassian/servers/dependencies.py:189–217) then uses this value directly as the url= parameter when constructing a JiraConfig and JiraFetcher. The first method call on the fetcher (get_current_user_account_id()) immediately issues a GET request to {header_url}/rest/api/2/myself — an outbound SSRF call to the attacker-controlled URL.

No comparison is made against the server-configured JIRA_URL environment variable. No private IP r…

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

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-2026-27826 has been found in mcp-atlassian.
Attackers can target a specific entry point like GET /rest/api/2/myself over the network to misuse the product.
Confidential information can be exposed externally.
What to do: upgrade mcp-atlassian to 0.17.0 or later.
If unsure, ask your IT team or search "mcp-atlassian CVE-2026-27826" on the vendor's site.

CVE-2026-27826 (mcp-atlassian) — CWE-918
Attack vector: adjacent-network / unauthenticated / no user interaction
Attack surface: GET /rest/api/2/myself / Authorization header / Authorization / JiraConfig
Patched: 0.17.0 — 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 GET /rest/api/2/myself without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of mcp-atlassian. Attack surface: GET /rest/api/2/myself / Authorization header / Authorization / JiraConfig.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to 0.17.0.

🛡️ 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 GET /rest/api/2/myself requests with malformed payloads or SQL meta-characters. 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
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
Hunt for indicators of compromise detect
```
grep 'GET /rest/api/2/myself' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'
```
アクセスログで GET /rest/api/2/myself への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。
3
Apply patch patch
```
Upgrade mcp-atlassian to 0.17.0
```
ステージング環境で 0.17.0 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と、Step 2 で見つけた異常検知の続報チェックを含めること。
4
Post-deployment verification verify
```
Replay attack against GET /rest/api/2/myself on staging to confirm patch closes the vector
```
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 Step 2 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

PyPI mcp-atlassian

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.17.0"}]}]

References

package github.com
web github.com
web github.com