How severe is CVE-2026-77258?

CVE-2026-77258 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-77258 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-77258?

CVE-2026-77258 affects Mcp-atlassian Mcp Atlassian. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-77258?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2026-77258 published?

CVE-2026-77258 was published on 2026-09-22 and last updated on 2026-09-29.

CVE-2026-77258

CVE-2026-77258 is a high-severity vulnerability in Mcp-atlassian Mcp Atlassian with a CVSS 3.x base score of 7.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: High (CVSS 3.x base score 7.7)
EPSS exploit prediction: 0% (26th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-22
Affected product: Mcp-atlassian Mcp Atlassian
Published: 2026-09-22
Last modified: 2026-09-29

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, upload_attachment in src/mcp_atlassian/confluence/attachments.py accepts a caller-controlled file_path and opens the selected server-local file without restricting it to the workspace. A permitted Confluence MCP caller can upload the file as an attachment and disclose data readable by the server process. This issue is fixed in version 0.22.0.

Frequently asked questions

What is CVE-2026-77258?: MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, upload_attachment in src/mcp_atlassian/confluence/attachments.py accepts a caller-controlled file_path and opens the selected server-local file without restricting it to the workspace. A permitted Confluence MCP caller can upload the file as an attachment and disclose data readable by the server process. This issue is fixed in version 0.22.0.
How severe is CVE-2026-77258?: CVE-2026-77258 has a CVSS 3.x base score of 7.7, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-77258 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (26th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-77258?: CVE-2026-77258 affects Mcp-atlassian Mcp Atlassian. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-77258?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2026-77258 published?: CVE-2026-77258 was published on 2026-09-22 and last updated on 2026-09-29.

References

Affected products (1)

cpe:2.3:a:mcp-atlassian:mcp_atlassian:*:*:*:*:*:*:*:*

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