CVE-2020-23884: A buffer overflow in Nomacs v3.15.0 allows attackers to cause a denial of service (DoS) via a crafted MNG file

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MEDIUM 5.5DOWNGRADE

CVE-2020-23884 is a medium-severity flaw (CVSS 5.5) affecting nomacs. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A buffer overflow in Nomacs v3.15.0 allows attackers to cause a denial of service (DoS) via a crafted MNG file.

Why this priority

Public exploit reference

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

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.0% (top 38%)
CISA exploited list	No
Weakness	CWE-120
Published	2021-11-10
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: nomacs

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

Am I affected?

Timeline

2021-11-10 22:15 UTCPublished CVE record published
2026-06-17 03:05 UTCUpdated Record last modified

nomacs nomacs DOWNGRADE

Affected: 3.15.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.15.0

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 3.15.0 (Debian / Ubuntu)

apt-cache madison nomacs sudo apt install nomacs=<VERSION_BEFORE_3.15.0> sudo apt-mark hold nomacs

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

dnf --showduplicates list nomacs sudo dnf downgrade nomacs-<VERSION_BEFORE_3.15.0> sudo dnf versionlock add nomacs

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-2020-23884?

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

Is CVE-2020-23884 being exploited?

CVE-2020-23884 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-2020-23884 affect?

CVE-2020-23884 affects nomacs. Severity is medium (CVSS 5.5). A buffer overflow in Nomacs v3.15.0 allows attackers to cause a denial of service (DoS) via a crafted MNG file.

How urgent is CVE-2020-23884?

Priority 40/100. Public exploit reference

References

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