CVE-2026-39420— MaxKB: Sandbox escape via LD_PRELOAD bypass
Quick assessment
Affected
1Panel-dev MaxKB
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
MaxKB是1Panel-dev开源的一款基于大语言模型和 RAG 的开源知识库问答系统。 MaxKB 2.7.1及之前版本存在安全漏洞，该漏洞源于沙箱保护机制不完整，可能导致具有工具执行权限的经过身份验证的用户逃逸沙箱，进而导致不受限制的远程代码执行和网络访问。
Possible ATT&CK Techniques 1 AI
T1610 · Deploy Container
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I. Basic Information for CVE-2026-39420
Vulnerability Information
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Vulnerability Title
MaxKB: Sandbox escape via LD_PRELOAD bypass
Source: CVE Program / CVE List V5
Vulnerability Description
MaxKB is an open-source AI assistant for enterprise. In versions 2.7.1 and below, an incomplete sandbox protection mechanism allows an authenticated user with tool execution privileges to escape the LD_PRELOAD-based sandbox. By env command the attacker can clear the environment variables and drop the sandbox.so hook, leading to unrestricted Remote Code Execution (RCE) and network access. MaxKB restricts untrusted Python code execution via the Tool Debug API by injecting sandbox.so through the LD_PRELOAD environment variable. This intercepts sensitive C library functions (like execve, socket, open) to restrict network and file access. However, a patch allowed the /usr/bin/env utility to be executed by the sandboxed user. When an attacker is permitted to create subprocesses, they can execute the env -i python command. The -i flag instructs env to completely clear all environment variables before running the target program. This effectively drops the LD_PRELOAD environment variable. The newly spawned Python process will therefore execute natively without any sandbox hooks, bypassing all network and file system restrictions. This issue has been fixed in version 2.8.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
保护机制失效
Source: CVE Program / CVE List V5
Vulnerability Title
MaxKB 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
MaxKB是1Panel-dev开源的一款基于大语言模型和 RAG 的开源知识库问答系统。 MaxKB 2.7.1及之前版本存在安全漏洞，该漏洞源于沙箱保护机制不完整，可能导致具有工具执行权限的经过身份验证的用户逃逸沙箱，进而导致不受限制的远程代码执行和网络访问。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| 1Panel-dev | MaxKB | < 2.8.0 | - |
|
II. Public POCs for CVE-2026-39420
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-39420 (2)
-
Release v2.8.0 · 1Panel-dev/MaxKB · GitHub x_refsource_MISC
-
Same Patch Batch · 1Panel-dev · 2026-04-14 · 10 CVEs total
| CVE-2026-39421 | 6.3 MEDIUM | MaxKB: Sandbox escape via ctypes and unhooked SYS_pkey_mprotect |
| CVE-2026-39418 | 5.0 MEDIUM | MaxKB: SSRF via sandbox network hook bypass |
| CVE-2026-39417 | 4.6 MEDIUM | MaxKB: RCE via MCP stdio command injection in workflow engine |
| CVE-2026-39419 | 3.1 LOW | MaxKB: Sandbox Result Validation Bypass via Tool Output Spoofing |
| CVE-2026-39424 | MaxKB has CSV Injection in its Application Chat Export Functionality | |
| CVE-2026-39423 | Stored XSS via Eval Injection in EchartsRander Component | |
| CVE-2026-39425 | MaxKB: Stored XSS via Unsanitized html_rander Tags in Markdown Rendering | |
| CVE-2026-39426 | MaxKB: Stored XSS via Unsanitized iframe_render Parsing | |
| CVE-2026-39422 | MaxKB has Stored XSS via ChatHeadersMiddleware |
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V. Comments for CVE-2026-39420
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