CVE-2015-5987
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 · uneditedBelkin F9K1102 2 devices with firmware 2.10.17 use an improper algorithm for selecting the ID value in the header of a DNS query, which makes it easier for remote attackers to spoof responses by predicting this value.
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 Belkin F9K1102 router firmware 2.10.17 uses a weak, predictable algorithm for generating DNS transaction IDs in query headers. This allows remote attackers to anticipate the ID value and forge malicious DNS responses, enabling DNS cache poisoning attacks to redirect user traffic.
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< 2.50\(aazi.0\)c0CVSS 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
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/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 checksWork through these to decide whether this CVE applies to you.
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Identify the device modelLog into the device admin interface or check the physical device label to confirm the model is Zyxel Gs1900 10hpAffected if The device is not a Zyxel Gs1900 10hp - this CVE does not apply
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Check the installed firmware versionAccess the router web interface (typically 192.168.1.1) and navigate to Status or Administration > Firmware section, or use the CLI command 'show version' if SSH/Telnet is availableAffected if Firmware version cannot be determined or is >= 2.50(aazi.0)c0 - the vulnerability may not be present
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Verify DNS service is enabledCheck the router configuration for DNS proxy, DNS relay, or DNS forwarding settings in the web interface under Network or LAN settingsAffected if DNS service is disabled - the attack surface may be reduced but the weak algorithm still exists in the firmware code
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Confirm version is within affected rangeCompare your firmware version number to the affected threshold: versions below 2.50(aazi.0)c0 are vulnerableAffected if Installed version is < 2.50(aazi.0)c0 AND DNS functionality is used on the device
The device is affected if it is a Zyxel Gs1900 10hp running firmware version lower than 2.50(aazi.0)c0 and has DNS proxy/relay/forwarding 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 data2.50
Update to patched firmware if released by Belkin; otherwise consider replacing affected devices or implementing network-level protections like DNSSEC validation and DNS firewalls to mitigate spoofing risk.
- Consultation3.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,592.
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Free · runs locallyCheck whether your project pulls in CVE-2015-5987 — 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-2015-5987 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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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.
- 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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