sooperset mcp-atlassian up to 0.21.x Attachment Upload upload_attachment attachments information disclosure

Summaryinfo

A vulnerability, which was classified as problematic, has been found in sooperset mcp-atlassian up to 0.21.x. This affects the function upload_attachment of the component Attachment Upload. This manipulation of the argument attachments causes information disclosure. The identification of this vulnerability is CVE-2026-77255. It is possible to initiate the attack remotely. There is no exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in sooperset mcp-atlassian up to 0.21.x. Affected by this vulnerability is the function upload_attachment of the component Attachment Upload. The manipulation of the argument attachments with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-77255 since 08/20/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

Upgrading to version 0.22.0 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• sooperset

Name

• mcp-atlassian

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21

Website

• Product: https://github.com/sooperset/mcp-atlassian/

CPE 2.3info

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CPE 2.2info

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