CVE-2020-25108
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 DNS response data length is not checked (it can be set to an arbitrary value from a packet). 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 · moderate confidenceThe DNS implementation in Nut/OS 5.1 fails to validate the data length field in incoming DNS responses. An attacker controlling a malicious DNS server or performing DNS spoofing can craft responses with arbitrary length values, causing buffer overflows that lead to denial of service or potentially remote code execution on the embedded device.
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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Identify the Nut/OS versionCheck the firmware version or system information of the Ethernut device. This may be available via the device's web interface, serial console, or by examining the firmware binary for version strings.Affected if The installed Nut/OS version is 5.1 or any earlier version (version <= 5.1).
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Verify DNS client/resolver is enabledExamine the Nut/OS configuration (typically in config.h or via menuconfig) to determine if the DNS resolver feature (CONFIG_DNS or similar) is compiled into the firmware.Affected if DNS support is enabled in the Nut/OS build configuration.
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Check for DNS server configurationReview the device's network configuration to identify the configured DNS server(s). This may be in the application code, DHCP response handling, or a static configuration file.Affected if The device uses a DNS server that could be controlled by an attacker or is susceptible to DNS spoofing (e.g., unvalidated or untrusted DNS servers).
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Inspect DNS response handling code (if source available)If you have access to the source code, review the DNS response parsing functions (typically in the Nut/Net or Nut/DNS modules) for bounds checking on the length field before copying data into buffers.Affected if The code lacks validation that the DNS response length fields do not exceed buffer sizes.
You are affected if your device runs Nut/OS version 5.1 or earlier with the DNS resolver feature enabled and processes DNS responses without validating 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 strict bounds checking on DNS response data lengths before copying data into buffers; validate that length values do not exceed allocated buffer sizes and are consistent with the DNS protocol specification.
- Consultation2.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,904.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-25108 — 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-2020-25108 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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