MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions
MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, OAuthConfig writes a plaintext fallback file containing access and refresh tokens under the user's .mcp-atlassian directory using process-default permissions. On systems with a permissive umask, same-group or other local users and processes can read the persisted tokens and reuse the associated Atlassian access. The advisory traces the vulnerable input and processing flow through OAuthConfig._save_tokens, ~/.mcp-atlassian/oauth-.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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-77250
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 15:50 UTC · Revision 1
Source evidence
MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions
core-osv · Original sourcePublished 22 Sept 2026, 17:51 UTC
MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, OAuthConfig writes a plaintext fallback file containing access and refresh tokens under the user's .mcp-atlassian directory using process-default permissions. On systems with a permissive umask, same-group or other local users and processes can read the persisted tokens and reuse the associated Atlassian access. The advisory traces the vulnerable input and processing flow through OAuthConfig._save_tokens, ~/.mcp-atlassian/oauth-.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.
osv:CVE-2026-77250
Complete source record
{
"id": "ca19daa96e0da99955f73645859810078d1ef3fcd8a881594f7ba0b8a58612a3",
"url": "https://osv.dev/vulnerability/CVE-2026-77250",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "MCP Atlassian: OAuth fallback token storage writes plaintext access and refresh tokens with group-readable permissions",
"summary": "MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, OAuthConfig writes a plaintext fallback file containing access and refresh tokens under the user's .mcp-atlassian directory using process-default permissions. On systems with a permissive umask, same-group or other local users and processes can read the persisted tokens and reuse the associated Atlassian access. The advisory traces the vulnerable input and processing flow through OAuthConfig._save_tokens, ~/.mcp-atlassian/oauth-.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.",
"evidence": "osv:CVE-2026-77250",
"products": [],
"severity": "medium",
"structured": {
"id": "CVE-2026-77250",
"aliases": [
"CVE-2026-77250",
"GHSA-g5xv-mhgm-v5f6",
"PYSEC-2026-4094"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/sooperset/mcp-atlassian",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "b041733473f95119dd539542a43c280737a8e460"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
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"introduced": "0"
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{
"fixed": "0.22.0"
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"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
{
"fixed": "b041733473f95119dd539542a43c280737a8e460"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "b041733473f95119dd539542a43c280737a8e460"
}
],
"source": "REFERENCES_TAG",
"original_tag": "v0.22.0"
},
{
"cpe": "cpe:2.3:a:mcp-atlassian:mcp_atlassian:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "0.22.0"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"v0.21.1",
"v0.21.0",
"v0.20.1",
"v0.20.0",
"v0.19.0",
"v0.18.1",
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"v0.6.0",
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77250.json"
}
}
],
"modified": "2026-10-28T02:30:37.090053982Z",
"provider": "osv",
"references": [
"https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77250.json",
"https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-g5xv-mhgm-v5f6",
"https://nvd.nist.gov/vuln/detail/CVE-2026-77250",
"https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460",
"https://github.com/sooperset/mcp-atlassian/pull/1448"
],
"provider_metadata": {
"cwe_ids": [
"CWE-312"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77250.json"
}
},
"related_cves": [
{
"value": "CVE-2026-77250",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 504299,
"published_at": "2026-09-22T17:51:02.674+00:00"
}