CVE-2021-31727: Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 where IOCTL's 0x80002014

Routine

HIGH 7.8DOWNGRADE

CVE-2021-31727 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 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.

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	0.4% (top 69%)
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-2021-31727?

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

Is CVE-2021-31727 being exploited?

CVE-2021-31727 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-2021-31727 affect?

CVE-2021-31727 affects antimalware. Severity is high (CVSS 7.8). 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 \.\Zeman

How urgent is CVE-2021-31727?

Priority 35/100. 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-2021-31728 HIGH 7.8 DOWNGRADE Incorrect access control in zam64.sys, zam32.sys in MalwareFox AntiMalware 2.74.0.150 allows a non-privileged
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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