CVE-2026-77261: mcp-atlassian SSRF Redirect Protection Bypass in Basic Auth and OAuth
Summary
CVE-2026-77261: MCP Atlassian: SSRF redirect protection missing for basic-auth and OAuth authentication branches. Affects mcp-atlassian versions < 0.22.0. Fixed in 0.22.0. How to fix ↓
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Background
mcp-atlassian is a Python package designed to facilitate interactions with Atlassian products, such as Jira and Confluence. It provides various authentication methods, including basic authentication and OAuth, to connect securely to Atlassian servers. However, a critical vulnerability has been identified that affects the security of these authentication methods, allowing potential Server-Side Request Forgery (SSRF) attacks.
Vulnerability Detail
The vulnerability arises from the absence of SSRF redirect protection in the basic authentication and OAuth branches of the mcp-atlassian package. The function _make_ssrf_safe_hook() is intended to block HTTP redirects to private or internal IP addresses by validating the Location header. However, this protection is only applied in the header-PAT authentication branch, leaving the basic auth and OAuth branches vulnerable. An attacker controlling an Atlassian instance can exploit this flaw to redirect requests to internal services, potentially exposing sensitive data such as AWS IAM credentials.
How To Fix
Latest published version: 0.23.1 as of 23 Oct 2026
pip install --upgrade "mcp-atlassian==0.23.1"Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
0.22.0
This is the first release that contains the fix.
pip install --upgrade "mcp-atlassian==0.22.0"Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Workaround
As a temporary workaround, you can modify the code in src/mcp_atlassian/servers/dependencies.py to include attach_ssrf_hook=True in the calls to _create_and_validate() for both the basic auth and OAuth branches. For example:
Branch 2 (basic auth) - add hook
return _create_and_validate(request, spec, user_config, "basic", user_email=user_email, attach_ssrf_hook=True)
Branch 3 (OAuth/PAT) - add hook
return _create_and_validate(request, spec, user_config, "oauth_pat", user_email=user_email, attach_ssrf_hook=True)
Conclusion
The mcp-atlassian package has a critical vulnerability (CVE-2026-77261) that affects basic authentication and OAuth methods, allowing SSRF attacks. It is essential to update to version 0.22.0 or later to mitigate this risk. Users should also consider implementing the provided workaround until they can upgrade.
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FAQ
CVE-2026-77261 is a vulnerability in the mcp-atlassian package that allows SSRF attacks due to missing redirect protection in basic auth and OAuth authentication methods.
You can use the Vulert playground at Vulert Scanner to check if your application is affected by this vulnerability without needing to sign up.
Server-Side Request Forgery (SSRF) is a security vulnerability that allows an attacker to send crafted requests from a vulnerable server to internal or external resources, potentially exposing sensitive information.
If an immediate upgrade is not possible, implement the suggested workaround by modifying the code to include SSRF protection in the affected branches.
The CVSS score of this vulnerability is 7.1, indicating a high severity level.
References
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