CVE-2020-7877: A buffer overflow issue was discovered in ZOOK solution(remote administration tool) through processing 'Connec

This month

HIGH 8.0DOWNGRADEDOWNGRADE

CVE-2020-7877 is a high-severity flaw (CVSS 8.0) affecting zook agent, zook viewer. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A buffer overflow issue was discovered in ZOOK solution(remote administration tool) through processing 'ConnectMe' command while parsing a crafted OUTERIP value because of missing boundary check. This vulnerability allows the attacker to execute remote arbitrary command.

Why this priority

High severity

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

Risk facts

CVSS score	8.0 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.8% (top 43%)
CISA exploited list	No
Weakness	CWE-120
Published	2021-09-07
Last modified	2026-06-17

Publisher (CNA): KrCERT/CC · Vendor: mastersoft

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

Am I affected?

Timeline

2021-09-07 12:15 UTCPublished CVE record published
2026-06-17 03:25 UTCUpdated Record last modified

mastersoft zook agent DOWNGRADE

Affected: 2.0.6.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0.6.1

1. Check installed version

apt-cache policy zook-agent || rpm -q zook-agent || zook-agent --version

2. No fixed release: DOWNGRADE to a release before 2.0.6.1 (Debian / Ubuntu)

apt-cache madison zook-agent sudo apt install zook-agent=<VERSION_BEFORE_2.0.6.1> sudo apt-mark hold zook-agent

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

dnf --showduplicates list zook-agent sudo dnf downgrade zook-agent-<VERSION_BEFORE_2.0.6.1> sudo dnf versionlock add zook-agent

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.

mastersoft zook viewer DOWNGRADE

Affected: 2.0.4.6

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.0.4.6

1. Check installed version

apt-cache policy zook-viewer || rpm -q zook-viewer || zook-viewer --version

2. No fixed release: DOWNGRADE to a release before 2.0.4.6 (Debian / Ubuntu)

apt-cache madison zook-viewer sudo apt install zook-viewer=<VERSION_BEFORE_2.0.4.6> sudo apt-mark hold zook-viewer

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

dnf --showduplicates list zook-viewer sudo dnf downgrade zook-viewer-<VERSION_BEFORE_2.0.4.6> sudo dnf versionlock add zook-viewer

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-2020-7877?

zook agent: downgrade or apply the listed mitigation; zook viewer: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-7877 being exploited?

CVE-2020-7877 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-2020-7877 affect?

CVE-2020-7877 affects zook agent, zook viewer. Severity is high (CVSS 8.0). A buffer overflow issue was discovered in ZOOK solution(remote administration tool) through processing 'ConnectMe' command while parsing a crafted OUTERIP value because of missing boundary check. This vulnerability allows the attacker to ex

How urgent is CVE-2020-7877?

Priority 42/100. High severity

References

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