Summary
MCP Atlassian: MCP HTTP Client Server-Local File Exfiltration via Unvalidated Attachment Upload Path
Impact
Vulnerability class: Unauthenticated server-side file exfiltration through an unvalidated path passed to an MCP attachment upload tool, combined with attacker-controlled service URL injection via HTTP request headers.
Who is impacted:
- Operators running
mcp-atlassianin HTTP transport mode (streamable-httporsse) on a network-reachable endpoint withREAD_ONLY_MODE=false(the default). This includes multi-tenant SaaS deployments, internal tooling servers exposed to a broader corporate network, and any cloud-hosted instance. - Users whose secrets are stored on the server filesystem are at risk of credential theft,
.envfiles, SSH private keys, cloud provider credentials (~/.aws/credentials), kubeconfig files, TLS certificates, and any other file readable by the process.
Constraints on exploitability:
- The server must be running in HTTP transport mode (not the default
stdiomode). READ_ONLY_MODEmust not be set totrue.- The attacker must be able to reach the
/mcpendpoint (adjacent network or internet, depending on deployment). - The SSRF domain allowlist (
MCP_ALLOWED_URL_DOMAINS) must permit the attacker's hostname, or the attacker must control a public domain that passes the IP blocklist check.
Despite these preconditions, all are met in documented production deployment configurations described in the project's own README and Helm chart.
Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.
CVE-2026-77246 has a CVSS score of 7.4 (High). The vector is reachable from an adjacent network, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.22.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-77246? CVE-2026-77246 is a high-severity path traversal vulnerability in mcp-atlassian (pip), affecting versions < 0.22.0. It is fixed in 0.22.0. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
- How severe is CVE-2026-77246? CVE-2026-77246 has a CVSS score of 7.4 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of mcp-atlassian are affected by CVE-2026-77246? mcp-atlassian (pip) versions < 0.22.0 is affected.
- Is there a fix for CVE-2026-77246? Yes. CVE-2026-77246 is fixed in 0.22.0. Upgrade to this version or later.
- Is CVE-2026-77246 exploitable, and should I be worried? Whether CVE-2026-77246 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-77246 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-77246? Upgrade
mcp-atlassianto 0.22.0 or later.