XSS Vulnerability in MCP Atlassian for Confluence and Jira
CVE-2026-77272

5.4MEDIUM

Key Information:

Vendor

Sooperset

Status
Mcp-atlassian
Vendor
CVE Published:
22 September 2026

What is CVE-2026-77272?

The MCP Atlassian server for Confluence and Jira contains a cross-site scripting vulnerability due to improper handling of the OAuth error query parameter in the CallbackHandler._send_response function. Before version 0.22.0, this parameter was interpolated into an HTML response without proper escaping, allowing attackers to craft malicious authorization callbacks. When exploited, this could lead to arbitrary script execution in the user's browser during the OAuth flow. Users are encouraged to upgrade to version 0.22.0 or later to mitigate this security risk.

Affected Version(s)

mcp-atlassian < 0.22.0

References

https://github.com/sooperset/mcp-atlassian/security/advis...
x_refsource_CONFIRM
https://github.com/sooperset/mcp-atlassian/pull/1448
x_refsource_MISC
https://github.com/sooperset/mcp-atlassian/commit/b041733...
x_refsource_MISC

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.