Vulnerability · Published Sep 22, 2026 · Assigned by GitHub_M

CVE-2026-77274MCP Atlassian: SSRF Protection Bypass

High 8.8

In plain English

A high-severity server-side request forgery in mcp-atlassian from sooperset. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 26% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.8High

Exploit odds (30 days)0.3%top 73.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
PyPI	mcp-atlassian	0.22.0	GHSA-hgcf-4mq8-5266
PyPI	mcp-atlassian	0.22.0	PYSEC-2026-4096

Affected products (as reported)

Vendor	Product	Versions
sooperset	mcp-atlassian	< 0.22.0

Weakness: CWE-918 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

References

https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266 x_refsource_CONFIRM
https://github.com/sooperset/mcp-atlassian/pull/1448 x_refsource_MISC
https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460 x_refsource_MISC
https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0 x_refsource_MISC