CVE-2026-77267

mcp-atlassian has an incomplete SSRF remediation

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the X-Atlassian-Jira-Url and X-Atlassian-Confluence-Url headers are processed by _process_authentication_headers and used to construct Atlassian fetchers without calling validate_url_for_ssrf. A caller who can set these headers can supply an internal or metadata-service URL and cause the server to send requests to that destination, bypassing the incomplete CVE-2026-27826 remediation. This issue is fixed in version 0.22.0.

Affected

sooperset · mcp-atlassian

CVSS v4.0 GITHUB

8.3 HIGHCVSS: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:X/V:X/RE:X/U:X

CVSS v4.0 GitHub

8.3 HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N

CVSS v3.1 NVD

6.5 MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

EPSS

0.29% chance of exploitation in the next 30 days, 21st percentile

Published

2026-09-22

Updated

2026-09-28

Proof-of-concept exploits (1)

• advisories/GHSA-5wf4-jqxh-8gm3

Security advisories

• sooperset/mcp-atlassian/security/advisories/GHSA-5wf4-jqxh-8gm3
• sooperset/mcp-atlassian/pull/1448

References

• CVE Record
• NVD entry