CVE-2026-77242
Received Received - Intake

SSRF Bypass in MCP Atlassian Server

Publication date: 2026-09-22

Last updated on: 2026-09-22

Assigner: GitHub, Inc.

Description
MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, validate_url_for_ssrf checks a hostname's resolved addresses, but Requests and urllib3 resolve the hostname again when connecting. A caller can use a short-lived DNS answer that is public during validation and private during connection, preserving unauthenticated access to internal or metadata endpoints despite the earlier CVE-2026-27826 remediation. The advisory traces the vulnerable input and processing flow through validate_url_for_ssrf, _check_dns_resolution, socket.getaddrinfo, and _make_ssrf_safe_hook, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

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Meta Information

Published
2026-09-22
Last Modified
2026-09-22
Generated
2026-09-22
AI Q&A
2026-09-22
EPSS Evaluated
N/A
NVD
CVE-2026-77242
EUVD
EUVD-2026-84627

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
atlassian mcp 0.22.0
sooperset mcp-atlassian 0.22.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-367 The product checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check.
CWE-918 The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

Attack-Flow Graph

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Executive Summary

CVE-2026-77242 is an incomplete fix for CVE-2026-27826 in the MCP Atlassian server. The original fix validated URLs to prevent SSRF by checking resolved IPs, but it did not pin the validated IP. This allows DNS rebinding attacks where a domain resolves to a public IP during validation but to a private or metadata IP during connection, bypassing SSRF protections.

Detection Guidance

To detect this vulnerability, monitor DNS resolution logs for discrepancies between validation and connection times. Check if requests to internal or metadata endpoints originate from domains resolving to public IPs during validation but private IPs during connection. Use tools like tcpdump or Wireshark to inspect network traffic for unexpected connections to internal services.

Impact Analysis

This vulnerability enables unauthenticated SSRF attacks, allowing attackers to access internal services or metadata endpoints despite previous protections. It could lead to unauthorized data access, service disruption, or further exploitation of internal systems.

Mitigation Strategies

Upgrade to mcp-atlassian version 0.22.0 or later to apply the DNS rebinding fix. Ensure SSRF protections are enforced by validating redirects and pinning DNS resolution. Review network logs for unauthorized access attempts to internal endpoints and block suspicious domains.

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