# CVE-2026-77242: MCP Atlassian SSRF validation bypass via DNS rebinding

Source: https://junglewise.ai/threats/cve-2026-77242-mcp-atlassian-is-a-model-context-protocol-mcp-server-for  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-77242 · Severity: high · CVSS 7.5 · Published 2026-09-22

MCP Atlassian is a Model Context Protocol server that integrates with Confluence and Jira for task automation. A flaw in SSRF (Server-Side Request Forgery) protection allows attackers to bypass validation checks by exploiting DNS rebinding—using a domain that resolves to a public address during validation but a private/internal address during actual connection. An attacker can gain unauthenticated access to internal endpoints and metadata services that should be protected.

Technologies: [Sooperset Mcp-Atlassian](https://junglewise.ai/threats/technologies/sooperset-mcp-atlassian). Vendors: [Sooperset](https://junglewise.ai/threats/vendors/sooperset).

## Quick answers

**Is CVE-2026-77242 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77242 being exploited in the wild.

**How severe is CVE-2026-77242?** High severity, with a CVSS score of 7.5, published 22 September 2026.

**Which products and versions are affected?** Sooperset Mcp-Atlassian before 0.22.0.

**Is there a fix for CVE-2026-77242?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-77242 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-77242?** Check whether you run Sooperset Mcp-Atlassian at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The validate_url_for_ssrf function resolves hostnames during validation but the underlying Requests and urllib3 libraries perform a second DNS resolution at connection time. An attacker can exploit this time-of-check-time-of-use (TOCTOU) window by serving a short-lived DNS answer that is public during validation and private during connection. The vulnerability affects the SSRF validation logic in _check_dns_resolution and _make_ssrf_safe_hook entry points. Version 0.22.0 fixes this by introducing SsrfPinningAdapter, which resolves each host exactly once and pins the connection to the validated address.

## Affected products

- sooperset mcp-atlassian before 0.22.0

## Timeline

- 2026-09-22: disclosed

## References

- [https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460](https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460)
- [https://github.com/sooperset/mcp-atlassian/pull/1448](https://github.com/sooperset/mcp-atlassian/pull/1448)

## Related threats

- [sooperset mcp-atlassian path traversal in validate_safe_path](https://junglewise.ai/threats/cve-2026-124503-a-vulnerability-was-identified-in-sooperset-mcp-atlassian-up-to)
- [MCP Atlassian insecure file permissions in OAuth token storage](https://junglewise.ai/threats/cve-2026-77256-mcp-atlassian-is-a-model-context-protocol-mcp-server-for)
- [MCP Atlassian HTTP transport authentication bypass](https://junglewise.ai/threats/cve-2026-77254-mcp-atlassian-is-a-model-context-protocol-mcp-server-for)
- [MCP Atlassian path traversal in attachment upload](https://junglewise.ai/threats/cve-2026-77258-mcp-atlassian-is-a-model-context-protocol-mcp-server-for)
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