Adaptive Security Appliance SoftwareOperating system · Cisco
CVE-2015-4321
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 · uneditedThe Unicast Reverse Path Forwarding (uRPF) implementation in Cisco Adaptive Security Appliance (ASA) Software 9.3(1.50), 9.3(2.100), 9.3(3), and 9.4(1) mishandles cases where an IP address belongs to an internal interface but is also in the ASA routing table, which allows remote attackers to bypass uRPF validation via spoofed packets, aka Bug ID CSCuv60724.
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 confidenceCisco ASA uRPF implementation fails to properly validate packets when an IP address belongs to an internal interface but also exists in the ASA routing table, allowing spoofed packets to bypass uRPF checks.
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
Adaptive Security Appliance SoftwareOperating system
= 9.3\(1.50\)= 9.3\(2.100\)= 9.3\(3\)= 9.4\(1\)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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- None
- Availability
- None
AV:N/AC:L/Au:N/C:P/I:N/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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Verify ASA software versionRun 'show version' or 'show version | include Cisco Adaptive Security' to display the installed ASA software version.Affected if The installed version equals 9.3(1.50), 9.3(2.100), 9.3(3), or 9.4(1).
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Confirm uRPF is enabled on interfacesRun 'show running-config | include ip verify unicast reverse-path' to list all interfaces where uRPF is configured.Affected if uRPF is enabled on one or more interfaces.
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Identify internal interface IP addressesRun 'show ip address' to list all configured interface IP addresses, noting those assigned to inside or internal interfaces.Affected if The ASA has internal interfaces with assigned IP addresses.
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Check routing table for internal interface IPsRun 'show route' to display the routing table and compare it against the internal interface IPs from the previous step.Affected if Any internal interface IP address also appears as a connected or static route in the routing table.
A user is affected if they run an affected ASA version (9.3.1.50, 9.3.2.100, 9.3.3, or 9.4.1), have uRPF enabled on at least one interface, and possess an internal interface IP address that is also present in the routing table.
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 dataApply Cisco ASA software updates that address this uRPF bypass vulnerability; verify uRPF functionality remains intact after patching.
Fix this in Adaptive Security Appliance Software
Scoped from the published advisory
- Consultation4.0 h
- Implementation3.0 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 $3,440.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2015-4321 — 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-2015-4321 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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