CVE-2026-77272CWE-79cross-site-scripting

CVE-2026-77272

Medium · published September 22, 2026

CVSS v3.1
5.4
EPSS
0%
Percentile
15.1
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.4 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00248 · 15.1th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-09-22T23:16Z
Affected products (1)
ProductVersionsFixed in
mcp-atlassian/mcp_atlassian< 0.22.00.22.0
References (4)
https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460 · [email protected]https://github.com/sooperset/mcp-atlassian/pull/1448 · [email protected]https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0 · [email protected]https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-g2r2-3j32-j27x · [email protected]
EPSS history
Timeline
  • 24 SEP 03:25Z
    EPSS moved — → 0%
    epss
  • 22 SEP 18:33Z
    MCP Atlassian: Reflected XSS in OAuth Setup Callback Handler
    cvelistv5