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CVE-2026-77256 Details

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the plaintext OAuth fallback file containing refresh and access tokens is written with permissions inherited from the process umask. Under common or permissive configurations, other local users can read the backup and retain Atlassian access through the refresh token. The advisory traces the vulnerable input and processing flow through OAuthConfig._save_tokens_to_file, refresh_token, access_token, and umask, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:6.5 MEDIUMVector:CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-76pr-5669-3xf5	CISA-ADP	MitigationVendor Advisory
https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460	[email protected]	Patch
https://github.com/sooperset/mcp-atlassian/pull/1448	[email protected]	Issue TrackingPatch
https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0	[email protected]	Release Notes
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-76pr-5669-3xf5	[email protected]	MitigationVendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-732	Incorrect Permission Assignment for Critical Resource	[email protected]

Affected Products

Product	Versions
mcp-atlassian mcp atlassian	< 0.22.0
CPE cpe:2.3:a:mcp-atlassian:mcp_atlassian:::::::: Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Sep 28, 2026	Initial Analysis	[email protected]
Sep 22, 2026	CVE Modified	CISA-ADP
Sep 22, 2026	New CVE Received	[email protected]