CVE-2026-77265
Received Received - Intake

SSRF via DNS Rebinding 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, header-supplied Jira or Confluence URLs are resolved and validated before the HTTP client resolves the hostname again for the connection. An unauthenticated caller can use a DNS-rebinding hostname that returns a public address during validation and an internal address during connection, causing requests to internal or metadata services. The advisory traces the vulnerable input and processing flow through X-Atlassian-Jira-Url, X-Atlassian-Confluence-Url, validate_url_for_ssrf, and DNS rebinding, 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-2026-77265
EUVD
EUVD-2026-84606

Affected Vendors & Products

Showing 2 associated CPEs
Vendor Product Version / Range
atlassian mcp 0.22.0
sooperset mcp-atlassian to 0.22.0 (exc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
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

This vulnerability is a Server-Side Request Forgery (SSRF) issue in the mcp-atlassian package affecting versions before 0.22.0. It occurs due to a DNS rebinding attack in header-based authentication. The SSRF protection validates a URL by resolving its hostname to a public IP first, but later the actual HTTP request uses the same hostname which may resolve to an internal IP address, bypassing the check.

Detection Guidance

Check if your mcp-atlassian version is below 0.22.0 using package managers like pip show mcp-atlassian or npm list mcp-atlassian. Monitor network traffic for unexpected internal requests or DNS rebinding patterns. Use tools like Wireshark or tcpdump to inspect HTTP headers for X-Atlassian-Jira-Url or X-Atlassian-Confluence-Url with suspicious hostnames.

Impact Analysis

An attacker could exploit this to access internal network resources or cloud metadata services by tricking the server into making requests to internal IPs like 127.0.0.1 or 169.254.169.254. This could lead to unauthorized data exposure or service interactions within your internal network.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive internal data or metadata services, potentially violating confidentiality requirements under GDPR and HIPAA. Unauthorized data exposure may result in compliance breaches and regulatory penalties.

Mitigation Strategies

Upgrade mcp-atlassian to version 0.22.0 or later immediately. If upgrading is not possible, disable header-based URL resolution for Jira or Confluence in the configuration. Implement network-level controls to block internal IP access from the mcp-atlassian service. Review and restrict DNS rebinding protections on your DNS servers.

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