CVE-2020-24334
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 · uneditedThe code that processes DNS responses in uIP through 1.0, as used in Contiki and Contiki-NG, does not check whether the number of responses specified in the DNS packet header corresponds to the response data available in the DNS packet, leading to an out-of-bounds read and Denial-of-Service in resolv.c.
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 confidenceThe DNS response parser in uIP (resolv.c) fails to validate that the number of DNS responses indicated in the packet header matches the actual response data present in the packet. This allows an attacker to trigger an out-of-bounds read by sending a DNS response with a response count that exceeds the available data, causing a denial of service.
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<= 1.0CVSS 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
- Low
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/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 if uIP DNS resolver is in useSearch codebase or firmware for 'resolv.c' or 'uIP' references, or check build files for inclusion of resolv.cAffected if The project uses the uIP networking stack with DNS resolution enabled
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Determine uIP versionCheck version.h, README, or version tag in the uIP source directory; compare against '<=1.0'Affected if The uIP version is 1.0 or earlier
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Verify DNS response handling code existsLocate resolv.c in the source tree and confirm the function that parses DNS responses (typically resolv_traceip or similar) is compiled into the firmware/binaryAffected if DNS response parser code is present and active in the build
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Inspect resolv.c for bounds validationExamine resolv.c for a check that validates the DNS response count in the packet header against the actual response data length before processing; look for code that compares the response count to available packet dataAffected if The code lacks a bounds check comparing the DNS header response count to actual response data present in the packet
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Confirm DNS client is enabledCheck configuration (such as uIP's config.h, Makefile, or build defines) for ENABLE_DNS or similar flags; verify the device/application actually uses DNS resolution at runtimeAffected if DNS client functionality is compiled in and actively used by the system
A system is affected if it uses uIP version 1.0 or earlier with the DNS resolver (resolv.c) compiled in, and the resolv.c code lacks validation that the DNS response count matches the available response data.
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 bounds checking in resolv.c to validate that the response count in the DNS header corresponds to actual response data before processing, and reject packets with mismatched counts.
- Consultation2.0 h
- Implementation3.0 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 $3,808.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-24334 — 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-2020-24334 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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