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Vulnerability · Published Sep 22, 2026 · Assigned by GitHub_M

CVE-2026-77265MCP Atlassian: SSRF via DNS Rebinding in Header-Based Authentication Flow

Medium 5.9

In plain English

A medium-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 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.9Medium
Exploit odds (30 days)0.3%top 78.2% 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, header-supplied Jira or Confluence URLs are resolved and validated before the HTTP client resolves the hostname again for the connection. An unauthenticated caller can use a DNS-rebinding hostname that returns a public address during validation and an internal address during connection, causing requests to internal or metadata services. The advisory traces the vulnerable input and processing flow through X-Atlassian-Jira-Url, X-Atlassian-Confluence-Url, validate_url_for_ssrf, and DNS rebinding, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
PyPImcp-atlassian0.22.0GHSA-49xv-9743-pw8w
PyPImcp-atlassian0.22.0PYSEC-2026-4083

Affected products (as reported)

VendorProductVersions
sooperset mcp-atlassian < 0.22.0

Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

References