PYPI · JULY 2026 · EARLY WARNING

Potential DNS-Rebinding Attack on mcp-atlassian PyPI Package

EARLY WARNING · UNCONFIRMED. This page describes a developing threat that 0Day surfaced from early signals and has not yet independently confirmed. Details may change. Always verify against the primary sources before acting.
CVE-2026-27826GHSA-489G-7RXV-6C8QGHSA-7R34-79R5-RCC9Severity: HIGH

An early warning has been issued regarding a potential DNS-rebinding attack on the mcp-atlassian package on PyPI, affecting versions ≥0.17.0.

What happened

The mcp-atlassian package on PyPI is under investigation for a DNS-rebinding TOCTOU bypass of the SSRF fix. This issue appears to allow unauthenticated SSRF attacks due to a lack of IP pinning when resolving the attacker-controlled X-Atlassian-{Jira,Confluence}-Url header host. The vulnerability is reportedly present in versions ≥0.17.0 of the package.

To assess your exposure, check if your projects or dependencies include mcp-atlassian version ≥0.17.0. It is recommended to monitor for a patch that properly pins the resolved IP to the connection to prevent DNS-rebinding attacks. For more detailed information, consult the primary sources listed in the threat data.

No definitive compromise has been confirmed, and the situation is still under investigation. It is crucial to stay updated with the latest advisories and patches from the primary sources to mitigate any potential risks.

How 0Day mitigates this

MATCHED TO YOUR ACTUAL DEPENDENCY GRAPH0Day matches every incoming threat signal against your GitHub organization’s full dependency graph, including transitive dependencies. If mcp-atlassian is anywhere in your dependency tree, the engineers who own the affected repositories get a push alert the moment it is flagged — no manual audit to remember to run.

Read how this differs from waiting on a scanner to catch a known advisory, or see the exact, read-only access 0Day needs to do this for an organization.

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