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UK Cyber Defence
VulnerabilityAnalyzed

CVE-2026-77242

The advisory traces the vulnerable input and processing flow through validate_url_for_ssrf, _check_dns_resolution, socket.getaddrinfo, and _make_ssrf_safe_hook, which identify the affected entry points, controls, and code paths.

HIGH 7.5EPSS 0.30%

Does this matter?

High impact if exploited, but EPSS currently rates exploitation as unlikely (0.30%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.

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 checks a hostname's resolved addresses, but Requests and urllib3 resolve the hostname again when connecting. A caller can use a short-lived DNS answer that is public during validation and private during connection, preserving unauthenticated access to internal or metadata endpoints despite the earlier CVE-2026-27826 remediation. The advisory traces the vulnerable input and processing flow through validate_url_for_ssrf, _check_dns_resolution, socket.getaddrinfo, and _make_ssrf_safe_hook, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

CVSS 3.1
7.5 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:L/A:N
EPSS
0.30% probability · 23th percentile
Public exploits
None in Exploit-DB
CISA KEV
Not listed
Weakness
CWE-367, CWE-918
Affected
mcp-atlassian/mcp atlassian
Source
security-advisories@github.com
EPSS trend
0%3%5%23 September 2026: 0.29%26 October 2026: 0.30%23 September 202626 October 2026

EPSS moved from 0.3% on 23 September 2026 to 0.3% on 26 October 2026.

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.