CVE-2026-77255

What it 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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data exposure.

Exploit odds

0.5% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-09-22 19:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-09-29 13:41 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.5% in the next 30 days (EPSS).
• Severity: 8.6 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-09-22 19:16 UTC

Last modified

2026-09-29 13:41 UTC

Exploit probability

0.5% · EPSS, next 30 days

Weakness

CWE-22 · Path traversal

Record status

Analyzed

Affected

• mcp-atlassian Mcp Atlassian < 0.22.0

Attack profile CVSS 3.1 · 8.6

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-77255.md and follow it. Check whether this project is affected by CVE-2026-77255. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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