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AntimalwareApplication · Malwarefox

CVE-2021-31727

HIGH · 7.8 CVSS v3.1 Published 2021-05-17
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 where IOCTL's 0x80002014, 0x80002018 expose unrestricted disk read/write capabilities respectively. A non-privileged process can open a handle to \.\ZemanaAntiMalware, register with the driver using IOCTL 0x80002010 and send these IOCTL's to escalate privileges by overwriting the boot sector or overwriting critical code in the pagefile.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A local privilege escalation vulnerability exists in MalwareFox AntiMalware's kernel drivers (zam32.sys/zam64.sys) where improper access control on IOCTL handlers 0x80002014 and 0x80002018 allows unprivileged processes to perform unrestricted disk read/write operations by registering with the driver via IOCTL 0x80002010. This enables attackers to overwrite boot sectors or inject malicious code into critical system areas.

MitigationThe vendor should implement proper privilege validation in the driver to ensure only appropriately authorized callers can access disk read/write IOCTLs. Users should update to a patched version or remove the software if no update is available.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
AntimalwareApplication
Affected:= 2.74.0.150

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify MalwareFox AntiMalware installation and version
    Check the installed version of MalwareFox AntiMalware by examining the program's version information in Add/Remove Programs, Program Files directory, or using system inventory tools. Compare the installed version to 2.74.0.150.
    Affected if The installed version is exactly 2.74.0.150.
  2. Locate kernel driver files
    Search for zam32.sys and zam64.sys files in system directories, typically found in C:\Windows\System32\drivers\ or within the MalwareFox installation directory.
    Affected if Either zam32.sys or zam64.sys file is present on the system.
  3. Check if driver is currently loaded
    Use tools such as 'driverquery' command, Process Explorer, or Registry keys under HKLM\SYSTEM\CurrentControlSet\Services to determine if zam32 or zam64 driver is loaded and running.
    Affected if The zam32.sys or zam64.sys driver is currently loaded in memory.
  4. Verify driver IOCTL interface accessibility
    Examine the driver's registered IOCTL handlers using kernel debugging tools or by analyzing driver communications. Specifically look for handlers at codes 0x80002014 and 0x80002018 that provide disk read/write capabilities.
    Affected if The IOCTL handlers 0x80002014 and 0x80002018 are accessible to unprivileged processes without proper authorization checks.

The system is affected if MalwareFox AntiMalware version 2.74.0.150 is installed with the zam32.sys or zam64.sys driver loaded, as this combination enables unprivileged disk access through the vulnerable IOCTL handlers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

The vendor should implement proper privilege validation in the driver to ensure only appropriately authorized callers can access disk read/write IOCTLs. Users should update to a patched version or remove the software if no update is available.

Fix this in Antimalware Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA3.0 h
19.0 hours of engineering $3,380
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-31727 in production — separate from our analysis above.

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What this is

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What belongs here
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