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NethackApplication

CVE-2020-5212

CRITICAL · 9.8 CVSS v3.1 Published 2020-01-28
Fix available
A fix is available. Upgrade to 3.6.5 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In NetHack before 3.6.5, an extremely long value for the MENUCOLOR configuration file option can cause a buffer overflow resulting in a crash or remote code execution/privilege escalation. This vulnerability affects systems that have NetHack installed suid/sgid and shared systems that allow users to upload their own configuration files. Users should upgrade to NetHack 3.6.5.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

NetHack before 3.6.5 contains a buffer overflow vulnerability in the parsing of the MENUCOLOR configuration file option. When an excessively long value is provided, it overflows a buffer, potentially allowing remote code execution or privilege escalation. This is particularly dangerous on systems where NetHack is installed with suid/sgid privileges or where users can upload custom configuration files.

MitigationUpgrade to NetHack 3.6.5 or later. On shared systems, restrict user ability to upload custom configuration files and consider removing suid/sgid bits from NetHack if not required.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
NethackApplication
Affected:< 3.6.5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine installed NetHack version
    Run 'nethack -version' or check your system package manager for the installed NetHack package version
    Affected if The installed version is lower than 3.6.5 (for example, 3.6.4, 3.6.3, etc.)
  2. Locate NetHack configuration files
    Look for .nethackrc in your home directory, check ~/.config/nethack/, or search for nethack.cnf in standard config directories
    Affected if You have custom NetHack configuration files present on the system
  3. Examine MENUCOLOR configuration entries
    Open any found NetHack configuration files and search for lines containing 'MENUCOLOR'
    Affected if MENUCOLOR entries are defined in your configuration file with values that could exceed normal expected length
  4. Check NetHack binary for elevated privileges
    Run 'ls -l' on the NetHack binary (commonly /usr/games/nethack or /usr/bin/nethack) to inspect file permissions
    Affected if The binary has suid or sgid bits set (permissions show 's' instead of 'x' in user or group position)

You are affected if your NetHack version is below 3.6.5 and you use custom configuration files that contain MENUCOLOR settings with long values, especially on systems where the NetHack binary has suid/sgid privileges.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 3.6.5 or later
Fixed in 3.6.5
Interim mitigation

Upgrade to NetHack 3.6.5 or later. On shared systems, restrict user ability to upload custom configuration files and consider removing suid/sgid bits from NetHack if not required.

Recommended fix High confidence

NetHack 3.6.5

  1. Identify the current NetHack version installed on the system using 'nethack --version' or checking the package manager
  2. Download NetHack 3.6.5 from the official GitHub repository or your distribution's package manager
  3. If using a package manager, update to version 3.6.5 (e.g., 'apt-get update && apt-get install nethack' or equivalent for your OS)
  4. If compiling from source, download the source code for version 3.6.5 and follow standard build procedures
  5. After installation, verify the new version is 3.6.5 or later
  6. If NetHack was installed with suid/sgid privileges, ensure proper permissions are maintained (chmod u+s/sg or equivalent)
  7. For shared systems, review and validate any user-supplied configuration files to prevent malicious MENUCOLOR entries
Caveat Standard upgrade - review release notes for any gameplay or configuration changes that may affect existing setups

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Nethack Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,984.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-5212 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data