CVE-2020-25110
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 · uneditedAn issue was discovered in the DNS implementation in Ethernut in Nut/OS 5.1. The length byte of a domain name in a DNS query/response is not checked, and is used for internal memory operations. This may lead to successful Denial-of-Service, and possibly Remote Code Execution.
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 confidenceA buffer overflow vulnerability exists in the DNS implementation of Nut/OS 5.1 used by Ethernut. The length byte of a domain name in DNS query/response messages is not validated before being used for internal memory operations, allowing an attacker to overflow buffers and potentially achieve remote code execution.
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<= 5.1CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Check Nut/OS firmware versionQuery the device or firmware for the Nut/OS version identifier. This is typically available through the device's system information, boot logs, or management interface.Affected if The installed Nut/OS version is 5.1 or any version prior to 5.1 (i.e., <= 5.1)
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Identify DNS service statusDetermine whether the DNS client or server functionality is enabled in the Nut/OS configuration. Check the Nut/OS configuration file (typically nutconf or a compiled configuration header) for DNS-related modules such as NutDns, NutDnsCache, or DNS client initialization code.Affected if DNS support is compiled into or enabled on the firmware
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Verify DNS domain name handlingIf source code is accessible, search for DNS message parsing functions that handle domain names. Look for code that processes the length byte from DNS packets without bounds validation before copying to internal buffers.Affected if Custom or unmodified DNS parsing code is in use that does not validate the domain name length byte before memory operations
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Check for exposed DNS interfacesIdentify if the device exposes DNS services to untrusted networks. Review network configuration to determine if the DNS client listens on accessible network interfaces where malicious DNS responses could be received.Affected if The DNS client can receive responses from untrusted or external network sources
The environment is affected if the device runs Nut/OS version 5.1 or lower AND has DNS functionality enabled, allowing it to process DNS responses with unvalidated domain name length fields.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataImplement proper bounds checking on the domain name length byte before using it in memory operations, then update the Nut/OS firmware on affected Ethernut devices.
- Consultation4.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA3.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,040.
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Free · runs locallyCheck whether your project pulls in CVE-2020-25110 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2020-25110 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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