Is CVE-2026-77272 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-77272?

CVE-2026-77272 has a CVSS v3 severity of MEDIUM (5.4).

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CVE-2026-77272

Description

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.