CVE-2020-24340
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 picoTCP and picoTCP-NG through 1.7.0. The code that processes DNS responses in pico_mdns_handle_data_as_answers_generic() in pico_mdns.c does not check whether the number of answers/responses specified in a DNS packet header corresponds to the response data available in the packet, leading to an out-of-bounds read, invalid pointer dereference, and Denial-of-Service.
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 confidenceIn picoTCP and picoTCP-NG through 1.7.0, the DNS response handler function pico_mdns_handle_data_as_answers_generic() in pico_mdns.c fails to validate that the answer count specified in the DNS packet header matches the actual response data available in the packet. This allows an attacker to trigger an out-of-bounds read and invalid pointer dereference by sending a DNS response with a mismatched answer count.
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<= 1.7.0<= 1.7.0CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 picoTCP is in useSearch your codebase, firmware, or dependencies for 'picoTCP' or 'pico_tcp' references. Check build files, libraries, and embedded firmware images for the picoTCP module.Affected if picoTCP or picoTCP-NG is present in your environment
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Determine the picoTCP versionCheck the version string in the library binary, source code version header, or firmware bill of materials. Look for version 1.7.0 or earlier.Affected if The installed version is 1.7.0 or lower
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Verify mDNS/DNS functionality is enabledCheck the build configuration or feature flags for picoTCP. Look for CONFIG_PICO_MDNS or similar mDNS-related compile-time options being enabled. Inspect the compiled binary for pico_mdns.c functions.Affected if mDNS (multicast DNS) support is compiled into the firmware or application
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Confirm DNS response processing is activeIdentify if your device or application acts as a DNS client or resolver that processes incoming DNS responses. Check network service configurations that use picoTCP for DNS or mDNS name resolution.Affected if The system processes DNS/mDNS responses from the network
You are affected if your environment uses picoTCP or picoTCP-NG version 1.7.0 or earlier with mDNS/DNS response processing enabled.
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 dataAdd bounds checking to verify the answer count in the DNS header against the available packet data before processing answers, and reject packets with insufficient data.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-24340 — 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-2020-24340 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
- No spam, self-promotion, credentials, or personal data