CVE-2020-5254: In NetHack before 3.6.6, some out-of-bound values for the hilite_status option can be exploited

Routine

LOW 3.9UPGRADE

CVE-2020-5254 is a low-severity flaw (CVSS 3.9) affecting nethack. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In NetHack before 3.6.6, some out-of-bound values for the hilite_status option can be exploited. NetHack 3.6.6 resolves this issue.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	3.9 (Low)
Attack vector	Local
Attack complexity	High
Privileges needed	Low
User interaction	Required
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Weakness	CWE-125, CWE-119
Published	2020-03-10
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: nethack

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

Am I affected?

Timeline

2020-03-10 17:15 UTCPublished CVE record published
2026-06-17 03:21 UTCUpdated Record last modified

nethack nethack UPGRADE

Affected: >= 3.6.1 and < 3.6.6

Fixed in: 3.6.6

Safe to downgrade to: a release before 3.6.1

1. Check installed version

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

2. UPGRADE to 3.6.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nethack

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nethack

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.6.1 (Debian / Ubuntu)

apt-cache madison nethack sudo apt install nethack=<VERSION_BEFORE_3.6.1> sudo apt-mark hold nethack

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list nethack sudo dnf downgrade nethack-<VERSION_BEFORE_3.6.1> sudo dnf versionlock add nethack

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-2020-5254?

nethack: upgrade to 3.6.6. Exact commands for each OS are on this page.

Is CVE-2020-5254 being exploited?

CVE-2020-5254 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-2020-5254 affect?

CVE-2020-5254 affects nethack. Severity is low (CVSS 3.9). In NetHack before 3.6.6, some out-of-bound values for the hilite_status option can be exploited. NetHack 3.6.6 resolves this issue.

How urgent is CVE-2020-5254?

Priority 30/100. No elevated risk signals yet.

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CVE-2020-5253 LOW 3.9 UPGRADE NetHack before version 3.6.0 allowed malicious use of escaping of characters in the configuration file (usuall
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CVE-2020-5213 MEDIUM 5.0 UPGRADE In NetHack before 3.6.5, too long of a value for the SYMBOL configuration file option can cause a buffer overf
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References

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