CVE-2026-77268 json
MCP Atlassian: Insecure File Permissions on OAuth Token Storage
published 2026-09-22 47 d ago modified 2026-10-01 38 d ago also EUVD-2026-84757 , GHSA-4596-2p6p-28cv , PYSEC-2026-4082
- cvss
- 5.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 4%
- public exploits
- 0
- none known
Summary
MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the OAuth fallback token directory and JSON file are created without explicit owner-only modes. Local users or processes with access through the resulting group or world permission bits can read access and refresh tokens and reuse the associated Atlassian session. The advisory traces the vulnerable input and processing flow through ~/.mcp-atlassian, oauth-<client_id>.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.
Patch / fix
- pypi mcp-atlassian 0.22.0
- sooperset mcp_atlassian 0.22.0
- mcp-atlassian mcp_atlassian 0.22.0
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 47 d ago
Exploit prediction
0.15% chance of exploitation in the next 30 days, higher than 4% of all scored CVEs (FIRST EPSS, 2026-11-08).
Exploits and checks
- github.com https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-4596-2p6p-28cv referenced PoC, tagged "exploit" by a source, unverified
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
| GitHub | 3.1 | 5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
| OSV | 3.1 | 5.5 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| pypi | mcp-atlassian | <0.22.0 |
0.22.0 |
Affected products
- sooperset mcp-atlassian
Classification
- Weakness
-
- CWE-732 Incorrect Permission Assignment for Critical Resource
References
-
github.com
/sooperset/mcp-atlassian/pull/1448
web, issue-tracking, patch
-
github.com
/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460
web, patch
-
github.com
/sooperset/mcp-atlassian/security/advisories/GHSA-4596-2p6p-28cv
web, exploit, mitigation, vendor-advisory
-
github.com
/sooperset/mcp-atlassian/releases/tag/v0.22.0
web, release-notes
-
github.com
/sooperset/mcp-atlassian
package
-
pypi.org
/project/mcp-atlassian
package
-
github.com
/advisories/GHSA-4596-2p6p-28cv
advisory
-
nvd.nist.gov
/vuln/detail/CVE-2026-77268
advisory
Sources
- CVE List CVE-2026-77268
- GitHub Advisory GHSA-4596-2p6p-28cv
- NVD CVE-2026-77268
- OSV PYSEC-2026-4082
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.