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Fencer Vulns
high 7.4

CVE-2026-77246 json

MCP Atlassian: MCP HTTP Client Server-Local File Exfiltration via Unvalidated Attachment Upload Path

published 2026-09-22 47 d ago modified 2026-10-01 38 d ago also GHSA-wv8v-v4c5-v75j , PYSEC-2026-4104 , EUVD-2026-84771

cvss
7.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, an HTTP transport deployment with READ_ONLY_MODE=false accepts a request without an Authorization identity and permits attacker-controlled Atlassian service headers, including X-Atlassian-Confluence-Url, to select a public attacker hostname or one allowed by MCP_ALLOWED_URL_DOMAINS. A caller can then invoke confluence_upload_attachment or the Jira attachment variant in src/mcp_atlassian/jira/attachments.py with a server-local file_path and cause the MCP process to send the file to the selected attachment endpoint. This issue is fixed in version 0.22.0.

Patch / fix

  • pypi mcp-atlassian 0.22.0
  • mcp-atlassian mcp_atlassian 0.22.0

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
45 d ago

Exploit prediction

0.47% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-wv8v-v4c5-v75j referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.4 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
NVD 3.1 8.6 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
OSV 3.1 7.4 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
GitHub 3.1 7.4 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
pypi mcp-atlassian
<0.22.0
0.22.0

Affected products

  • sooperset mcp-atlassian

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory
  • CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
  • CWE-441 Unintended Proxy or Intermediary

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.