MaxKB: Sandbox escape via LD_PRELOAD bypass

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Summary

CVECVE-2026-39420
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-14 01:16:04 UTC
Updated2026-04-20 17:35:22 UTC
DescriptionMaxKB 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.

Risk And Classification

Primary CVSS: v3.1 7.4 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

EPSS: 0.001710000 probability, percentile 0.383520000 (date 2026-04-20)

Problem Types: CWE-78 | CWE-693 | CWE-693 CWE-693: Protection Mechanism Failure | CWE-78 CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7.4HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L
3.1[email protected]Secondary6.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
3.1CNADECLARED6.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Maxkb Maxkb All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA 1Panel-dev MaxKB affected < 2.8.0 Not specified

References

ReferenceSourceLinkTags
github.com/1Panel-dev/MaxKB/commit/2d17b08e6b060329803754a05e806d0ddecf3fa8 [email protected] github.com Patch
github.com/1Panel-dev/MaxKB/releases/tag/v2.8.0 [email protected] github.com Release Notes
github.com/1Panel-dev/MaxKB/security/advisories/GHSA-7wgv-v2r3-7f7w [email protected] github.com Vendor Advisory
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