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UipApplication · Uip Project

CVE-2020-17439

HIGH · 8.3 CVSS v3.1 Published 2020-12-11
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
92/100
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
An issue was discovered in uIP 1.0, as used in Contiki 3.0 and other products. The code that parses incoming DNS packets does not validate that the incoming DNS replies match outgoing DNS queries in newdata() in resolv.c. Also, arbitrary DNS replies are parsed if there was any outgoing DNS query with a transaction ID that matches the transaction ID of an incoming reply. Provided that the default DNS cache is quite small (only four records) and that the transaction ID has a very limited set of values that is quite easy to guess, this can lead to DNS cache poisoning.

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

The DNS parser in uIP 1.0 (resolv.c) fails to validate that incoming DNS replies correspond to outgoing queries, and accepts any reply whose transaction ID matches an outstanding query. Combined with a small DNS cache (4 records) and predictable transaction IDs, attackers can easily poison the DNS cache by sending malicious replies with matching transaction IDs.

MitigationImplement proper query-reply validation (matching source IP, destination port, and query details) and improve transaction ID randomization. Consider increasing DNS cache size to reduce poisoning predictability.

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
UipApplication
Affected:= 1.0

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
Changed
Confidentiality
Low
Integrity
Low
Availability
Low

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

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. Identify uIP DNS resolver in use
    Search the codebase for resolv.c or resolv.h files from the uIP project. Check project dependencies and source file listings for the presence of uIP 1.0 DNS resolver components.
    Affected if The codebase contains uIP 1.0 resolv.c (DNS resolver)
  2. Verify DNS resolution is enabled
    Locate the uIP configuration header (commonly uip-conf.h or similar) and check if DNS resolution feature is enabled. Look for compile-time flags such as UIP_DNS or RESOLV_CONF.
    Affected if DNS resolution (resolv.c) is compiled and actively used in the firmware/application
  3. Check DNS cache size configuration
    Examine the resolv.c source code or configuration files for the DNS cache size. Look for definitions of RESOLV_MAX_ENTRIES, RESOLV_ENTRIES, or similar constants that define how many DNS records can be cached.
    Affected if The DNS cache is configured to 4 records (small cache increases poisoning predictability)
  4. Examine transaction ID handling
    Review the resolv.c source code for how transaction IDs are generated and validated. Check if the ID is sourced from a predictable counter or weak randomness rather than secure random generation.
    Affected if Transaction IDs are generated using predictable or insufficiently randomized methods
  5. Verify query-reply validation
    Inspect the resolv.c code path that processes incoming DNS responses. Look for validation logic that verifies the response matches the original query details (query name, type, class) in addition to transaction ID matching.
    Affected if Incoming DNS replies are accepted based solely on matching transaction ID without validating query details

A system is affected if it uses uIP 1.0 with the DNS resolver enabled, particularly when the cache size is small (4 records) and transaction IDs are predictably generated without proper query-reply validation.

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

Implement proper query-reply validation (matching source IP, destination port, and query details) and improve transaction ID randomization. Consider increasing DNS cache size to reduce poisoning predictability.

Fix this in Uip Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
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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-2020-17439 in production — separate from our analysis above.

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