Wide Area Application ServicesApplication · Cisco
CVE-2015-6421
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 · uneditedcifs-ao in the CIFS optimization functionality on Cisco Wide Area Application Service (WAAS) and Virtual WAAS (vWAAS) devices 5.x before 5.3.5d and 5.4 and 5.5 before 5.5.3 allows remote attackers to cause a denial of service (resource consumption and device reload) via crafted network traffic, aka Bug ID CSCus85330.
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 denial of service vulnerability exists in the cifs-ao (CIFS acceleration optimization) component of Cisco Wide Area Application Services (WAAS) and Virtual WAAS. Remote attackers can send crafted network traffic to trigger excessive resource consumption, causing the device to reload unexpectedly.
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
= 5.1.1= 5.1.1a= 5.1.1b= 5.1.1c= 5.1.1d= 5.2.1= 5.2_base= 5.3.1= 5.3.3= 5.3.5= 5.3.5a= 5.3.5bCVSS 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:3.0/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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Confirm Cisco WAAS installationRun 'show version' or 'show software version' on the device CLI to identify if Cisco WAAS or vWAAS software is runningAffected if The device is running Cisco WAAS or Virtual WAAS software
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Check WAAS software versionExamine the version output from 'show version' and compare it to the affected list: 5.1.1, 5.1.1a, 5.1.1b, 5.1.1c, 5.1.1d, 5.2.1, 5.2_base, 5.3.1, 5.3.3, 5.3.5, 5.3.5a, 5.3.5bAffected if The installed version matches one of these specific versions
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Verify CIFS acceleration optimization is enabledRun 'show running-config' or look for CIFS-related configuration using 'show service cifs' or 'show cifs' commands. Search for 'cifs-ao' or 'cifs acceleration' in the configurationAffected if The CIFS acceleration optimization (cifs-ao) feature is enabled in the configuration
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Check for CIFS traffic handlingInspect active CIFS connections and traffic statistics using 'show statistics cif' or similar CIFS monitoring commandsAffected if CIFS traffic is being processed by the WAAS device
The environment is affected if the device runs a vulnerable Cisco WAAS/vWAAS version (5.1.1 through 5.3.5b) with the CIFS acceleration optimization (cifs-ao) feature enabled and handling CIFS traffic.
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/vWAAS to version 5.3.5d or later for the 5.x branch, or 5.5.3 or later for the 5.5 branch. If upgrading is not immediately feasible, consider disabling CIFS optimization or restricting CIFS traffic to trusted sources at upstream network boundaries.
Fix this in Wide Area Application Services
Scoped from the published advisory
- Consultation6.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,336.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-6421 — 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-2015-6421 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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