XSS in Mcp-Atlassian 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 · last modified .
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
EPSS: 0.003 (18.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 18th percentile — 18.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.000
Affected products
- Mcp-Atlassian Mcp Atlassian
- Sooperset Mcp-Atlassian — versions < 0.22.0
Weakness classification (CWE)
References
- github.com/sooperset/mcp-atlassian/security/advisories/GHSA-g2r2-3j32-j27x (Exploit, Vendor Advisory)
- github.com/sooperset/mcp-atlassian/pull/1448 (Patch, Issue Tracking)
- github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e… (Patch)
- github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0 (Release Notes)
Frequently asked questions
- What is CVE-2026-77272?
- CVE-2026-77272 is a medium-severity vulnerability in Mcp-Atlassian 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.