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CVE-2026-77242

MCP Atlassian: Incomplete fix for CVE-2026-27826: DNS rebinding bypasses SSRF validation (validated IP not pinned)

7.5 High

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
Low
Availability
None

Exploit likelihood

0.30%Unchanged since Sep 23, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.5

MCP Atlassian: Incomplete fix for CVE-2026-27826: DNS rebinding bypasses SSRF validation (validated IP not pinned)

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.

Record
CVE-2026-77242
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-367, CWE-918
Updated
2026-11-02
EUVDEUVD-2026-84627 7.5

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.

Record
EUVD-2026-84627
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N
Updated
2026-11-02
NVD 7.5

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.

Record
CVE-2026-77242
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-367, CWE-918
Updated
2026-11-02
OSV 7.5

MCP Atlassian: Incomplete fix for CVE-2026-27826: DNS rebinding bypasses SSRF validation (validated IP not pinned)

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.

Record
CVE-2026-77242
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-367, CWE-918
Updated
2026-11-02

Affected products

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-77242 is a high vulnerability (CVSS 7.5) in Mcp-atlassian Mcp Atlassian, published September 22, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.30%, the 22nd percentile. No source names a fixed version.

References

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