sooperset mcp-atlassian up to 0.21.x OAuth Token Saving OAuthConfig._save_tokens_to_file refresh_token/access_token missing encryption

Summaryinfo

A vulnerability has been found in sooperset mcp-atlassian up to 0.21.x and classified as problematic. The impacted element is the function OAuthConfig._save_tokens_to_file of the component OAuth Token Saving. The manipulation of the argument refresh_token/access_token leads to missing encryption. This vulnerability is referenced as CVE-2026-77256. The attack can only be performed from a local environment. No exploit is available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in sooperset mcp-atlassian up to 0.21.x. It has been rated as problematic. This issue affects the function OAuthConfig._save_tokens_to_file of the component OAuth Token Saving. The manipulation of the argument refresh_token/access_token with an unknown input leads to a missing encryption vulnerability. Using CWE to declare the problem leads to CWE-311. The product does not encrypt sensitive or critical information before storage or transmission. Impacted is confidentiality. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-77256 since 08/20/2026. The exploitation is known to be difficult. Attacking locally is a requirement. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1600 according to MITRE ATT&CK.

Upgrading to version 0.22.0 eliminates this vulnerability.

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Productinfo

Type

• Artificial Intelligence Software

Vendor

• sooperset

Name

• mcp-atlassian

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21

Website

• Product: https://github.com/sooperset/mcp-atlassian/

CPE 2.3info

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CPE 2.2info

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