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CVE-2026-77272

MCP Atlassian: Reflected XSS in OAuth Setup Callback Handler

CVSS 3.1 5.4 MEDIUMCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-77272

Published

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the OAuth error query parameter is passed to CallbackHandler._send_response in oauth_setup.py and interpolated into an HTML page without escaping. A crafted authorization callback can inject markup or script that executes in the browser of a user completing the OAuth flow. This issue is fixed in version 0.22.0.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-77272

Published

mcp-atlassian

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "sooperset",
                    "product": "mcp-atlassian",
                    "versions": [
                        {
                            "version": "< 0.22.0",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON