What is CVE-2026-77272?

CVE-2026-77272 is a medium-severity vulnerability in Sooperset Mcp-Atlassian, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-09-22.

How severe is CVE-2026-77272?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Sooperset Mcp-Atlassian

CVE-2026-77272

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2026-09-22.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N.

EPSS exploit prediction

No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.

Affected products

Sooperset Mcp-Atlassian — versions < 0.22.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

Frequently asked questions

What is CVE-2026-77272?: CVE-2026-77272 is a medium-severity vulnerability in Sooperset Mcp-Atlassian, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-09-22.
How severe is CVE-2026-77272?: Medium severity. CVSS v3 base score is 5.4 out of 10.