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CVE-2026-77251 medium CVSS 6.5

Vulnerability in mcp-atlassian (CVE-2026-77251)

Summary

Vulnerability in mcp-atlassian (CVE-2026-77251). Confidential information can be exposed externally. Exploitable via JIRA_PROJECTS_FILTER. Mitigation: upgrade to 0.22.0 or later.

Original description

The description as published by the source.

Summary

mcp-atlassian is a popular community MCP server wrapper exposing Jira / Confluence to MCP clients. Operators commonly restrict the surface to a small allowlist of projects/spaces via the JIRA_PROJECTS_FILTER and CONFLUENCE_SPACES_FILTER environment variables, which the README documents as the principal mechanism for limiting attacker-controlled MCP clients (= prompt-injected LLM agents) to the operator's intended subset of the workspace.

We identified three distinct sub-bugs that let attacker-controlled queries read content from forbidden projects/spaces (= projects NOT in the operator's filter) despite the filter being correctly set. The most severe is empirically reproduced on production Atlassian Cloud with real operator credentials and sentinel content in two real projects.

Sub-bug Layer Class Live?
A1 Jira jira_search jql substring-bypass 🔴 LIVE PROVEN 2026-05-18 on real Atlassian Cloud
A2 Confluence confluence_search cql case-sensitive substring-bypass code-level verified
B Jira agile get_board_issues / get_agile_boards zero-filter (missing check) code-level verified

Details

Sub-bug A1 — src/mcp_atlassian/jira/search.py lines 92-94 at HEAD d8bc78698a63cb6b321c7ca796d6329d448f7f6d:

if projects_filter and "project = " not in jql.lower():
    jql = f"{jql} AND project in ({','.join(projects_filter)})"

The substring check is s…

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-2026-77251 has been found in mcp-atlassian.
Attackers can target a specific entry point like JIRA_PROJECTS_FILTER 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-2026-77251" on the vendor's site.

CVE-2026-77251 (mcp-atlassian) — CWE-184 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: JIRA_PROJECTS_FILTER / CONFLUENCE_SPACES_FILTER / jira_search / jql
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

A vulnerability (CWE-184) exists in mcp-atlassian. Attackers reach the vulnerable code path via JIRA_PROJECTS_FILTER.

📍 Affected scope

Check the vendor advisory for the affected versions of mcp-atlassian. Attack surface: JIRA_PROJECTS_FILTER / CONFLUENCE_SPACES_FILTER / jira_search / jql.

🔥 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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