Wide Area Application ServicesApplication · Cisco
CVE-2017-6721
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 · uneditedA vulnerability in the ingress processing of fragmented TCP packets by Cisco Wide Area Application Services (WAAS) could allow an unauthenticated, remote attacker to cause the WAASNET process to restart unexpectedly, causing a denial of service (DoS) condition. More Information: CSCvc57428. Known Affected Releases: 6.3(1). Known Fixed Releases: 6.3(0.143) 6.2(3c)6 6.2(3.22).
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 confidenceA vulnerability in the ingress processing of fragmented TCP packets in Cisco Wide Area Application Services (WAAS) allows an unauthenticated remote attacker to send specially crafted fragmented TCP packets that cause the WAASNET process to restart unexpectedly, resulting in 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
Wide Area Application ServicesApplication
= 6.3\(1\)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
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 checksWork through these to decide whether this CVE applies to you.
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Identify WAAS software versionExecute 'show version' or 'show waas version' on the Cisco WAAS device CLI to retrieve the installed software version numberAffected if The version displayed equals 6.3(1)
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Confirm WAASNET process statusExecute 'show processes' or check the WAAS Central Manager console to verify the WAASNET process is currently runningAffected if WAASNET process is active and the version is 6.3(1)
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Verify network accessibility of WAAS interfaceReview network interface configuration using 'show interface' or check ACLs to determine if the WAAS device is directly reachable from untrusted networksAffected if The WAAS device management or data interface is exposed to external networks where attackers could send fragmented TCP packets
If the installed WAAS version is exactly 6.3(1) and the device is network-accessible, the environment is vulnerable to CVE-2017-6721 and the WAASNET process can be crashed via crafted fragmented TCP packets.
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 dataUpgrade Cisco WAAS to a fixed release (6.3(0.143), 6.2(3c)6, or 6.2(3.22)). Until patching is possible, consider network-level filtering of suspicious fragmented TCP traffic or implementing rate limiting as a temporary mitigation.
Fix this in Wide Area Application Services
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-6721 — 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-2017-6721 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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- Version or environment caveats, and links to real fixes
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