CVE-2026-77274: mcp atlassian SSRF — Exploit & Fix

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, validate_url_for_ssrf has a backslash authority confusion because it interprets the authority differently from the Requests connection layer in the header-based Jira and Confluence URL authentication flow. A crafted URL can validate as an external hostname while the HTTP client connects to an internal host, permitting server-side requests to protected network resources. This issue is fixed in version 0.22.0.

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CVSS v3.1 Score

8.2

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

EPSS — Exploit Prediction

0.0032

Probability of exploitation

0.24%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-918 Server-Side Request Forgery (SSRF)

Affected Products

Vendor	Product	Versions
mcp-atlassian	mcp_atlassian	< 0.22.0

References

Advisories & Patches

https://github.com/sooperset/mcp-atlassian/commit/b041733473f95119dd539542a43c280737a8e460 https://github.com/sooperset/mcp-atlassian/pull/1448 https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266 https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266

Exploits

https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266 https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-hgcf-4mq8-5266

Other References

https://github.com/sooperset/mcp-atlassian/releases/tag/v0.22.0

Frequently Asked Questions

What is CVE-2026-77274? +

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, validate_url_for_ssrf has a backslash authority confusion because it interprets the authority differently from the Requests connection layer in the header-based Jira and Confluence URL authentication flow. A crafted URL can validate as an external hostname while the HTTP client connects to an internal host, permitting server-side requests to protected network resources. This issue is fixed in version 0.22.0. It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-77274? +

CVE-2026-77274 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0032, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-77274? +

CVE-2026-77274 affects products from mcp-atlassian, specifically: mcp_atlassian. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-77274? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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