# CVE-2026-77261: MCP Atlassian SSRF protection bypass in basic-auth and OAuth branches

Source: https://junglewise.ai/threats/cve-2026-77261-mcp-atlassian-ssrf-protection-bypass-in-basic-auth-and-oauth  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-22. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-77261 · Severity: high · CVSS 7.1 · Published 2026-09-22

MCP Atlassian is a connector used by Claude to integrate with Jira and other Atlassian products. A security control designed to prevent server-side request forgery (SSRF) attacks is missing from the basic authentication and OAuth credential paths, even though it correctly protects the API token path. An attacker who compromises an Atlassian server can redirect requests from the MCP connector to internal cloud services—such as AWS metadata endpoints—to steal credentials or access internal infrastructure.

Technologies: [mcp-atlassian (PyPI)](https://junglewise.ai/threats/technologies/mcp-atlassian). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2026-77261 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-77261 being exploited in the wild.

**How severe is CVE-2026-77261?** High severity, with a CVSS score of 7.1, published 22 September 2026.

**Which products and versions are affected?** mcp-atlassian (PyPI) < 0.22.0, ECOSYSTEM:introduced=0,fixed=0.22.0.

**Is there a fix for CVE-2026-77261?** Yes. mcp-atlassian (PyPI): upgrade to 0.22.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-77261 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-77261?** Check whether you run mcp-atlassian (PyPI) 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.

## How to fix

- mcp-atlassian (PyPI): upgrade to 0.22.0 or later

  ```sh
  pip install "mcp-atlassian>=0.22.0"
  ```


## Technical details

The vulnerability is an incomplete fix for a prior SSRF issue (GHSA-7r34-79r5-rcc9). The `_make_ssrf_safe_hook()` function validates HTTP `Location` headers in 3xx redirects and blocks requests to private IP addresses. However, this hook is only attached when using header-based PAT authentication; basic auth and OAuth authentication branches call `_create_and_validate()` without the `attach_ssrf_hook=True` parameter, leaving those codepaths unprotected. An attacker controlling or compromising an Atlassian server can return a 302 redirect to a private address (e.g., 169.254.169.254 AWS metadata, internal Kubernetes API, or database) and the unhooked session will follow it, exfiltrating credentials or internal data. The fix is straightforward: add `attach_ssrf_hook=True` to the two affected `_create_and_validate()` calls in the basic auth and OAuth branches.

## Affected products

- Anthropic MCP Atlassian 0.21.1 and earlier

## Identifiers

- CVE-2026-77261
- GHSA-6529-c226-h328
- PYSEC-2026-4085

## Timeline

- 2026-09-22: disclosed: GHSA-6529-c226-h328 published

## Related threats

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- [Atlassian MCP insecure OAuth token file permissions](https://junglewise.ai/threats/cve-2026-77268-atlassian-mcp-insecure-oauth-token-file-permissions)
- [MCP Atlassian path traversal in upload_attachment](https://junglewise.ai/threats/cve-2026-77266-mcp-atlassian-path-traversal-in-upload-attachment)
- [sooperset mcp-atlassian path traversal in confluence_upload_attachment](https://junglewise.ai/threats/cve-2026-77262-sooperset-mcp-atlassian-path-traversal-in-confluence-upload)