CVE-2026-77272
MCP Atlassian: Reflected XSS in OAuth Setup Callback Handler
MEDIUM 6.1EPSS 0.2%
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.
- Affected
- sooperset · mcp-atlassian
- CVSS v3.1 NVD
- 6.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS v3.1 GITHUB
- 5.4 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N - EPSS
- 0.25% chance of exploitation in the next 30 days, 15th percentile
- Published
- 2026-09-22
- Updated
- 2026-09-23