CVE-2021-31728: Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 allows a non-privileged

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HIGH 7.8DOWNGRADE

CVE-2021-31728 is a high-severity flaw (CVSS 7.8) affecting antimalware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 allows a non-privileged process to open a handle to \.\ZemanaAntiMalware, register itself with the driver by sending IOCTL 0x80002010, allocate executable memory using a flaw in IOCTL 0x80002040, install a hook with IOCTL 0x80002044 and execute the executable memory using this hook with IOCTL 0x80002014 or 0x80002018, this exposes ring 0 code execution in the co

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	3.4% (top 11%)
CISA exploited list	No
Published	2021-05-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: malwarefox

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-05-17 13:15 UTCPublished CVE record published
2026-06-17 03:52 UTCUpdated Record last modified

malwarefox antimalware DOWNGRADE

Affected: 2.74.0.150

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.74.0.150

1. Check installed version

apt-cache policy antimalware || rpm -q antimalware || antimalware --version

2. No fixed release: DOWNGRADE to a release before 2.74.0.150 (Debian / Ubuntu)

apt-cache madison antimalware sudo apt install antimalware=<VERSION_BEFORE_2.74.0.150> sudo apt-mark hold antimalware

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list antimalware sudo dnf downgrade antimalware-<VERSION_BEFORE_2.74.0.150> sudo dnf versionlock add antimalware

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-31728?

antimalware: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-31728 being exploited?

CVE-2021-31728 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-31728 affect?

CVE-2021-31728 affects antimalware. Severity is high (CVSS 7.8). Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 allows a non-privileged process to open a handle to \.\ZemanaAntiMalware, register itself with the driver by sending IOCTL 0x80002010, allocate executable

How urgent is CVE-2021-31728?

Priority 50/100. High severity

Related CVEs

CVE-2024-6260 HIGH 7.8 DOWNGRADE Malwarebytes Antimalware Link Following Local Privilege Escalation Vulnerability
CVE-2022-42045 MEDIUM 6.7 DOWNGRADE DOWNGRADE Certain Zemana products are vulnerable to Arbitrary code injection
CVE-2021-31727 HIGH 7.8 DOWNGRADE Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 where IOCTL's 0x80002014
CVE-2019-6739 HIGH 8.8 DOWNGRADE This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Malwarebyt
CVE-2019-6440 CRITICAL 9.8 DOWNGRADE Zemana AntiMalware before 3.0.658 Beta mishandles update logic.

References

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