---
title: "CVE-2026-27825: MCP Atlassian has an arbitrary file write leading to arbitrary code execution via unconstrained download_path in confluence_download_attachment"
url: https://erroneo.us/security/cve/CVE-2026-27825/
description: "CVE-2026-27825 (mcp-atlassian (PyPI)): MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-03-10
date_modified: 2026-03-10
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-27825"
kev: false
cvss: 9.1
epss: 0.01529
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-27825: MCP Atlassian has an arbitrary file write leading to arbitrary code execution via unconstrained download_path in confluence_download_attachment

**Signal:** Critical, preconditions apply. Severe if exploited, but exploitation needs conditions that may not apply to you. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Not in CISA KEV , but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 1.5% , percentile 74: FIRST’s model estimates a 1.5% chance of exploitation activity in the next 30 days, higher than 74% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes mcp-atlassian (PyPI) < 0.17.0, fixed in 0.17.0 . Check your lockfile, including transitive dependencies.

## What it is

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version 0.17.0, the confluencedownloadattachment MCP tool accepts a downloadpath parameter that is written to without any directory boundary enforcement. An attacker who can call this tool and supply or access a Confluence attachment with malicious content can write arbitrary content to any path the server process has write access to. Because the attacker controls both the write destination and the written content (via an uploaded Confluence attachment), this constitutes for arbitrary code execution (for example, writing a valid cron entry to /etc/cron.d/ achieves code execution within one scheduler cycle with no server restart required). Version 0.17.0 fixes the issue.

## Affected packages

- PyPI `mcp-atlassian` < 0.17.0 → fixed: 0.17.0

## Affected products (CVE record)

- sooperset mcp-atlassian: < 0.17.0

## Severity

- GitHub_M CVSS 3.1: 9.1 `CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`
- GitHub CVSS 3.1: 9.0 `CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H`

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 1.53% probability of exploitation activity in the next 30 days; percentile 74.

## Sources

- [GitHub Advisory GHSA-xjgw-4wvw-rgm4](https://github.com/advisories/GHSA-xjgw-4wvw-rgm4)
- [CVE.org record CVE-2026-27825](https://www.cve.org/CVERecord?id=CVE-2026-27825)
- [NVD entry CVE-2026-27825](https://nvd.nist.gov/vuln/detail/CVE-2026-27825)
- [github.com](https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-xjgw-4wvw-rgm4)
- [github.com](https://github.com/sooperset/mcp-atlassian/commit/52b9b0997681e87244b20d58034deae89c91631e)

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Source page: https://erroneo.us/security/cve/CVE-2026-27825/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt