JetBrains Junie CLI: Code execution via untrusted project MCP server configuration
Summary
JetBrains Junie CLI, a command-line AI coding agent, is affected before version 26.8.3. Junie CLI can execute code based on the MCP server configuration of an untrusted project. An attacker who gets a user to open or work with a malicious project can run code with that user's privileges. The attack is local and requires user interaction, and CVSS 3.1 rates the impact on confidentiality, integrity and availability as high.
Affected
- JetBrains Junie CLI before 26.8.3 (affected range 0 to < 26.8.3 per the CVE record)
Fixed in
- Fixed in JetBrains Junie CLI 26.8.3 (per the CVE record and VulDB).
- Later Junie CLI builds are reported with newer fixes; verify the current release with JetBrains.
Workaround
- No vendor workaround is documented beyond upgrading.
- Until upgraded, do not launch Junie CLI in untrusted repositories and review project-level MCP configuration (.junie/mcp/mcp.json) before first use. This is practical advice from the research, not from a source.
Exploitation
- CISA SSVC assessment: exploitation none, automatable no, technical impact total.
- VulDB states that no exploit is available.
- No public exploitation or proof of concept was found in the research; this is not a confirmed negative.
Our recommendation
- Inventory systems with Junie CLI and check the installed version.
- Upgrade to 26.8.3 or newer, and check JetBrains for the current build.
- Review MCP configuration before working with untrusted repositories.
- Prioritise machines that hold production credentials or access shared code.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- JetBrains: Fixed security issues www.jetbrains.com
- VulDB: CVE-2026-111091 vuldb.com
- OpenCVE: CVE-2026-111091 app.opencve.io
- Vulners: CVE-2026-111091 vulners.com
- JetBrains: Junie CLI MCP configuration junie.jetbrains.com
- JetBrains blog: Junie CLI inside your JB IDE blog.jetbrains.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 1 Nov 2026, 23:55.
Original description (NVD)
In JetBrains Junie CLI before 26.8.3 code execution was possible via an untrusted project's MCP server configuration
NVD references (1)
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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