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Vulnerability record · CVE-2026-77242 · published 22 September 2026

CVE-2026-77242: TOCTOU race condition vulnerability

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.

7.5 CVSS 3.1 High EPSS 0.29% · top 80.4% CWE-367 · TOCTOU race conditionCWE-918 · Server-side request forgery (SSRF) Undergoing Analysis
7.5CVSS 3.1 base score
0.29%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
23 Sep 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N

References

LinkTags
https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
https://github.com/sooperset/mcp-atlassian/pull/1448
https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-72fm-whvq-jghf
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-72fm-whvq-jghf

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Source: NIST National Vulnerability Database (record CVE-2026-77242), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.