CVE-2020-17467
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 FNET through 4.6.4. The code for processing the hostname from an LLMNR request doesn't check for '\0' termination. Therefore, the deduced length of the hostname doesn't reflect the correct length of the actual data. This may lead to Information Disclosure in _fnet_llmnr_poll in fnet_llmnr.c during a response to a malicious request of the DNS class IN.
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 confidenceFNET through 4.6.4 fails to verify null termination ('\0') when parsing hostnames from incoming LLMNR requests in fnet_llmnr.c. This causes the length calculation to exceed actual data bounds, potentially exposing heap/stack memory contents when responding to malicious LLMNR queries.
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<= 4.6.4CVSS 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
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/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 FNET version in useSearch the codebase for version definition files (such as fnet.h or version.h) and locate the version constant (commonly FNET_VERSION or similar). Compare the version number against the affected range: any version 4.6.4 or earlier is potentially vulnerable.Affected if FNET version is 4.6.4 or lower
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Verify LLMNR feature is enabledSearch project configuration files, build settings, or source code for the LLMNR feature flag (typically named FNET_CFG_LLMNR or FNET_LLMNR_ENABLED). Check if it is set to enabled or 1.Affected if LLMNR support is compiled or configured as enabled
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Confirm fnet_llmnr.c is in the buildVerify that the file fnet_llmnr.c exists in the project source tree and is included in the compilation. This file contains the vulnerable hostname parsing logic.Affected if The LLMNR source file is present and part of the build
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Check if LLMNR listener is activeInspect runtime configuration or initialization code to determine whether the LLMNR service is being started or registered. Look for calls to _fnet_llmnr_init or similar initialization functions that activate LLMNR query handling.Affected if LLMNR service initialization occurs and the application listens for LLMNR queries
You are affected if your FNET version is 4.6.4 or earlier AND LLMNR support is enabled and actively parsing incoming hostname data from LLMNR requests.
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 dataUpdate to FNET 4.6.5 or later which includes proper null terminator validation, or implement bounds checking on hostname length before use in _fnet_llmnr_poll to ensure only null-terminated string data is processed.
- Consultation2.0 h
- Implementation4.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-17467 — 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-2020-17467 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
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