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CVE-2026-77254

Mcp-atlassian Mcp Atlassian authentication bypass

9.1 CRITICALPublic exploitEPSS 0.62%
  1. Published22 Sept 2026

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, requests to the HTTP MCP endpoint without a per-user identity are allowed to reach tool handlers, which then use globally configured Jira or Confluence credentials. A network caller can perform operations with the operator account's permissions unless the deployment has an independent authentication boundary. The advisory traces the vulnerable input and processing flow through streamable-http, UserTokenMiddleware, _get_fetcher, and global credentials, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Mcp-atlassian Mcp Atlassian< 0.22.0

Remediation

Fixed in
Mcp-atlassian Mcp Atlassian≥ 0.22.0

References

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Frequently asked

Is CVE-2026-77254 being actively exploited?

CVE-2026-77254 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.62%.

How severe is CVE-2026-77254?

CVE-2026-77254 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.62% probability of exploitation.

Which products are affected by CVE-2026-77254?

Affected products include Mcp-atlassian Mcp Atlassian.

How do I fix CVE-2026-77254?

Upgrade affected software to a fixed version, for example Mcp-atlassian Mcp Atlassian 0.22.0 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-77254 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.