dbcve.org
Nichestack Tcp\/ipApplication · Hcc Embedded

CVE-2020-25926

HIGH · 7.5 CVSS v3.1 Published 2021-08-18
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
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
The DNS client in InterNiche NicheStack TCP/IP 4.0.1 is affected by: Insufficient entropy in the DNS transaction id. The impact is: DNS cache poisoning (remote). The component is: dns_query_type(). The attack vector is: a specific DNS response packet.

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 confidence

The DNS client in InterNiche NicheStack TCP/IP 4.0.1 uses a predictable transaction ID when issuing DNS queries in dns_query_type(). Insufficient entropy in the ID allows an attacker to forge DNS responses and poison the cache, redirecting domain resolutions to attacker-controlled addresses.

MitigationReplace the DNS transaction ID generation with a cryptographically secure random number generator to ensure unpredictability. Validate DNS responses using additional checks beyond transaction ID (e.g., source IP verification).

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
Nichestack Tcp\/ipApplication
Affected:= 4.0.1

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
None
Integrity
High
Availability
None

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

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. Verify NicheStack TCP/IP version
    Identify the version of InterNiche NicheStack TCP/IP in your environment. Check firmware images, library files, or source code imports for version string '4.0.1' or confirm your deployed version matches the affected release.
    Affected if Your environment uses NicheStack TCP/IP version 4.0.1 specifically.
  2. Confirm DNS client functionality is enabled
    Determine whether the DNS client module is compiled into or enabled for your application. This may involve checking build configurations, linker maps, or feature flags that include DNS resolution capabilities.
    Affected if DNS client is enabled and your application performs domain name resolution.
  3. Locate the dns_query_type function
    Review the NicheStack source code and locate the dns_query_type() function. This is where DNS queries are constructed and issued.
    Affected if The dns_query_type function exists in your codebase and is being used.
  4. Examine transaction ID generation code
    Within dns_query_type(), inspect how the DNS transaction ID is generated. Look for the variable or function used to populate the ID field in the DNS query packet.
    Affected if The transaction ID is generated using a predictable method such as a simple counter, static value, or low-entropy source.
  5. Check the RNG implementation for the transaction ID
    Identify what random number generator or entropy source is used for the transaction ID. Look for calls to RNG functions, random(), or similar within the ID generation logic.
    Affected if No cryptographically secure RNG is used, or the entropy source is insufficient/predictable.

You are affected if your environment runs NicheStack TCP/IP 4.0.1 with the DNS client enabled and the transaction ID generation in dns_query_type() lacks proper cryptographic randomness.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Replace the DNS transaction ID generation with a cryptographically secure random number generator to ensure unpredictability. Validate DNS responses using additional checks beyond transaction ID (e.g., source IP verification).

Fix this in Nichestack Tcp\/ip Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2020-25926 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2020-25926 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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