CVE-2026-77274

MCP Atlassian: SSRF Protection Bypass

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, validate_url_for_ssrf has a backslash authority confusion because it interprets the authority differently from the Requests connection layer in the header-based Jira and Confluence URL authentication flow. A crafted URL can validate as an external hostname while the HTTP client connects to an internal host, permitting server-side requests to protected network resources. This issue is fixed in version 0.22.0.

Affected

sooperset · mcp-atlassian

CVSS v4.0 GITHUB

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

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

CVSS v3.1 NVD

8.2 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS

0.32% chance of exploitation in the next 30 days, 24th percentile

Published

2026-09-22

Proof-of-concept exploits (1)

• advisories/GHSA-hgcf-4mq8-5266

Security advisories

• sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266
• sooperset/mcp-atlassian/pull/1448

References

• CVE Record
• NVD entry