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CVE-2026-77255

MCP Atlassian: Arbitrary File Read & Exfiltration (Confused Deputy) in JIRA update_issue

CVSS 3.1 8.6 HIGHCheck source for fixed versionsKEV status unknown

Original advisory

Historical advisory recorded 23 Oct 2026 15:48:27 UTC. Read the latest advisory.

cve-program · CVE-2026-77255

Published

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the Jira update_issue attachments argument is converted into local paths and routed to the attachment upload implementation without workspace validation. A caller can make the MCP server read arbitrary local files and attach them to a Jira issue, using the server as a confused deputy to exfiltrate the contents. The advisory traces the vulnerable input and processing flow through jira update_issue, attachments, upload_attachment, and file_path, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-77255

Published

mcp-atlassian

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "sooperset",
                    "product": "mcp-atlassian",
                    "versions": [
                        {
                            "version": "< 0.22.0",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON