CVE-2026-77268

MEDIUM 5.5

MCP Atlassian: Insecure File Permissions on OAuth Token Storage

CVSS Score

5.5

EPSS Score

0.0%

EPSS Percentile

0th

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the OAuth fallback token directory and JSON file are created without explicit owner-only modes. Local users or processes with access through the resulting group or world permission bits can read access and refresh tokens and reuse the associated Atlassian session. The advisory traces the vulnerable input and processing flow through ~/.mcp-atlassian, oauth-<client_id>.json, access_token, and refresh_token, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

CWE	CWE-732
Vendor	sooperset
Product	mcp-atlassian
Published	Sep 22, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Affected Versions

sooperset / mcp-atlassian

< 0.22.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-4596-2p6p-28cv github.com: https://github.com/sooperset/mcp-atlassian/pull/1448 github.com: https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460 github.com: https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0