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Vulnerability record · CVE-2026-77256 · published 22 September 2026

CVE-2026-77256: Incorrect permission assignment vulnerability

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.

8.3 CVSS 4.0 High EPSS 0.41% · top 67.7% CWE-732 · Incorrect permission assignment Undergoing Analysis
8.3CVSS 4.0 base score
0.41%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
5References
23 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
https://github.com/sooperset/mcp-atlassian/pull/1448
https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-76pr-5669-3xf5
https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-76pr-5669-3xf5

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Source: NIST National Vulnerability Database (record CVE-2026-77256), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.