CVE-2026-27826
MCP Atlassian has SSRF via unvalidated X-Atlassian-Jira-Url / X-Atlassian-Confluence-Url headers
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.
INFO
Published Date :
March 10, 2026, 7:17 p.m.
Last Modified :
April 13, 2026, 3:01 p.m.
Remotely Exploit :
No
Source :
[email protected]
Affected Products
The following products are affected by CVE-2026-27826
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update MCP Atlassian to version 0.17.0 or later.
- Ensure appropriate authentication controls are in place.
- Monitor network traffic for suspicious outbound requests.
Public PoC/Exploit Available at Github
CVE-2026-27826 has a 2 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27826.
| URL | Resource |
|---|---|
| https://github.com/sooperset/mcp-atlassian/commit/5cd697dfce9116ef330b8dc7a91291640e0528d9 | Patch |
| https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-7r34-79r5-rcc9 | Vendor Advisory Exploit |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27826 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27826
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Security gateway for MCP traffic. 5 built-in rules block prompt injection, credential leakage, path traversal, cross-repo exfiltration, and destructive commands. One pip install, zero config.
mcp security python proxy claude ai-agents prompt-injection self-hosted model-context-protocol llm-security ai-security cursor security-tools path-traversal credential-leakage
Python
Sentinel Skill for Claude
Python
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27826 vulnerability anywhere in the article.
-
The Hacker News
Actively Exploited nginx-ui Flaw (CVE-2026-33032) Enables Full Nginx Server Takeover
A recently disclosed critical security flaw impacting nginx-ui, an open-source, web-based Nginx management tool, has come under active exploitation in the wild. The vulnerability in question is CVE-20 ... Read more
The following table lists the changes that have been made to the
CVE-2026-27826 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Apr. 13, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N Added CPE Configuration OR *cpe:2.3:a:sooperset:mcp_atlassian:*:*:*:*:*:*:*:* versions up to (excluding) 0.17.0 Added Reference Type GitHub, Inc.: https://github.com/sooperset/mcp-atlassian/commit/5cd697dfce9116ef330b8dc7a91291640e0528d9 Types: Patch Added Reference Type GitHub, Inc.: https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-7r34-79r5-rcc9 Types: Exploit, Vendor Advisory -
New CVE Received by [email protected]
Mar. 10, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:A/AC:L/PR:N/UI:N/S:C/C:H/I:L/A:N Added CWE CWE-918 Added Reference https://github.com/sooperset/mcp-atlassian/commit/5cd697dfce9116ef330b8dc7a91291640e0528d9 Added Reference https://github.com/sooperset/mcp-atlassian/security/advisories/GHSA-7r34-79r5-rcc9