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Public proof of conceptFix available

CVE-2026-77266

A public proof of concept exists; no exploitation attested.

  • Published2026-09-22
  • Fixed in0.22.0
  • WeaknessCWE-22

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, upload_attachment accepts absolute paths and traversal sequences without constraining the resolved path to the server workspace. An MCP caller with attachment access can read a chosen server-local file and exfiltrate it through Jira or Confluence. The advisory traces the vulnerable input and processing flow through upload_attachment, file_path, and path traversal, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Timeline

dates in UTC
  1. 2026-09-2219:16CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-77266?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-77266?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Mcp-atlassian mcp atlassian
BranchAffectedFixed in
0.22< 0.22.00.22.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Mcp-atlassian mcp atlassian to 0.22.0

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • NVDCVE recordread 2026-10-23
  • CISA-ADPSSVC decisionpoc2026-09-22
  • OpenCVESSVC decisionpoc—
  • CNACVSS 3.16.5read 2026-10-23
  • CNAweakness (CWE)CWE-22read 2026-10-23
  • FIRST EPSSEPSS score0.4 %2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Published
2026-09-22
Last Modified
2026-09-28
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-77266?

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, upload_attachment accepts absolute paths and traversal sequences without constraining the resolved path to the server workspace. An MCP caller with attachment access can read a chosen server-local file and exfiltrate it through Jira or Confluence. The advisory traces the vulnerable input and processing flow through upload_attachment, file_path, and path traversal, which identify the affected entry points, controls, and code paths. This issue is fixed in version 0.22.0.

Is CVE-2026-77266 actively exploited?

A proof-of-concept exploit exists for CVE-2026-77266, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-77266?

CVE-2026-77266 has a CVSS v3 base score of 6.5 (MEDIUM severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N.

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