CVE-2026-39421Network attack vector

Authenticated code execution via unhooked pkey_mprotect syscall

Published Apr 14, 2026 · Updated Apr 14, 2026

Sandbox escape in FIT2CLOUD MaxKB 2.7.1 and earlier allows remote authenticated users to execute code through ToolExecutor. The LD_PRELOAD sandbox intercepts mprotect but not pkey_mprotect, so ctypes can allocate memory, mark it executable, and issue raw kernel system calls outside the user-space hooks. Workspace privileges and tool-execution access are required; successful exploitation permits network exfiltration and arbitrary code execution inside the MaxKB container.

CVSS severity6.3
Medium
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Sandbox escape in FIT2CLOUD MaxKB 2.7.1 and earlier allows remote authenticated users to execute code through ToolExecutor. The LD_PRELOAD sandbox intercepts mprotect but not pkey_mprotect, so ctypes can allocate memory, mark it executable, and issue raw kernel system calls outside the user-space hooks. Workspace privileges and tool-execution access are required; successful exploitation permits network exfiltration and arbitrary code execution inside the MaxKB container.

The record

CVE
CVE-2026-39421
Published
Apr 14, 2026
Updated
Apr 14, 2026
Vendor
KubeOperator
Product
MaxKB
Classifications
CWE-94, CWE-693, T1611
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Apr 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 2.8.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

KubeOperator · MaxKBversion=< 2.8.0

Published CVSS scores

6.3GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
7.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:L

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-94Improper Control of Generation of Code ('Code Injection')
CWE-693Protection Mechanism Failure
T1611Escape to Host

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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