TI-2026-53940 Aliases CVE-2026-77256

MCP Atlassian: OAuth refresh-token backup file is world-readable under default Unix umask

HIGH 69CWE-732Published 2026-09-22 · Updated 2026-09-22

Key facts

Attack vector: Network
Privileges required: Low
User interaction: None
Attack complexity: Low
Attack requirements: None
Impact type: —
Confidentiality · integrity · availability: High · None · None
Fix status: Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

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.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV

EPSS 0.00347 28th percentileScored 2026-11-07

Fix Fixed mcp-atlassian (sooperset): 0.22.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: Poc
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
sooperset	mcp-atlassian	before 0.22.0	0.22.0	Patch available	CNA

mcp-atlassian Vendorsooperset Affected before 0.22.0 Fixed in 0.22.0 Patch available CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:mcp-atlassian:mcp_atlassian::::::::	before 0.22.0	Vulnerable	Mcp-atlassian

cpe:2.3:a:mcp-atlassian:mcp_atlassian:*:*:*:*:*:*:*:* Versions before 0.22.0 Vulnerable ·Mcp-atlassian

Remediation

Fix · CNA mcp-atlassian (sooperset) Fixed in 0.22.0

Timeline

2026-10-02 Threatist record created from CVE-2026-77256

References

Patch 2

Advisory 1

https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-76pr-5669-3xf5

Other 1

https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0

TI-2026-53938 MCP Atlassian: Unauthenticated HTTP MCP requests can use globally configured Jira and Confluence credentials CVSS 3.1CRITICAL 9.1
TI-2026-53957 MCP Atlassian: SSRF Protection Bypass CVSS 4.0HIGH 8.8
TI-2026-53935 Protection mechanism failure in sooperset mcp-atlassian CVSS 4.0HIGH 8.3
TI-2026-53946 Path traversal in sooperset mcp-atlassian CVSS 3.1HIGH 8.6
TI-2026-53932 Path traversal in sooperset mcp-atlassian CVSS 3.1HIGH 8.6
TI-2026-22177 Path traversal in sooperset mcp-atlassian CVSS 3.1CRITICAL 9.1

See all 33 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences