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Public proof of conceptFix available

CVE-2026-27826

A public proof of concept exists; no exploitation attested.

  • Published2026-03-10
  • Fixed in0.17.0
  • WeaknessCWE-918

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 version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP headers without an `Authorization` header. No authentication is required. The vulnerability exists in the HTTP middleware and dependency injection layer — not in any MCP tool handler - making it invisible to tool-level code analysis. In cloud deployments, this could enable theft of IAM role credentials via the instance metadata endpoint (`169[.]254[.]169[.]254`). In any HTTP deployment it enables internal network reconnaissance and injection of attacker-controlled content into LLM tool results. Version 0.17.0 fixes the issue.

Timeline

dates in UTC
  1. 2026-03-1019:17CVE 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-2026-27826?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-27826?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Sooperset mcp atlassian
BranchAffectedFixed in
0.17< 0.17.00.17.0

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

Fix

  1. Update Sooperset mcp atlassian to 0.17.0

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

  • CISA-ADPSSVC decisionpoc2026-03-10
  • OpenCVESSVC decisionpoc—
  • CNACVSS 3.18.2read 2026-10-23
  • NVDCVSS 3.18.2read 2026-10-23
  • CNAweakness (CWE)CWE-918read 2026-10-23
  • FIRST EPSSEPSS score1.0 %2026-10-23
  • OSVaffected packages—

Technical details

CVSS v3 Vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N
Published
2026-03-10
Last Modified
2026-06-17
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-27826?

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to version 0.17.0, an unauthenticated attacker who can reach the mcp-atlassian HTTP endpoint can force the server process to make outbound HTTP requests to an arbitrary attacker-controlled URL by supplying two custom HTTP headers without an `Authorization` header. No authentication is required. The vulnerability exists in the HTTP middleware and dependency injection layer — not in any MCP tool handler - making it invisible to tool-level code analysis. In cloud deployments, this could enable theft of IAM role credentials via the instance metadata endpoint (`169[.]254[.]169[.]254`). In any HTTP deployment it enables internal network reconnaissance and injection of attacker-controlled content into LLM tool results. Version 0.17.0 fixes the issue.

Is CVE-2026-27826 actively exploited?

A proof-of-concept exploit exists for CVE-2026-27826, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-27826?

CVE-2026-27826 has a CVSS v3 base score of 8.2 (HIGH severity), with vector string CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N.

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