iOSOperating system · Cisco
CVE-2002-2053
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 design of the Hot Standby Routing Protocol (HSRP), as implemented on Cisco IOS 12.1, when using IRPAS, allows remote attackers to cause a denial of service (CPU consumption) via a router with the same IP address as the interface on which HSRP is running, which causes a loop.
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 · moderate confidenceHSRP (Hot Standby Routing Protocol) in Cisco IOS 12.1 has a design weakness where an attacker using IRPAS tools can introduce a rogue router with the same IP address as the active HSRP interface. This creates a routing loop between the legitimate router and the attacker-controlled router, causing excessive CPU consumption and 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
iOSOperating system
= 12.1CVSS 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
- None
- Integrity
- None
- Availability
- Partial
AV:N/AC:L/Au:N/C:N/I:N/A:P
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 IOS versionRun 'show version' and examine the firmware version string. Look for '12.1' in the version number.Affected if The device is running Cisco IOS version 12.1 (any subversion).
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Verify HSRP is enabledRun 'show standby' or 'show standby brief' to list all interfaces configured with HSRP.Affected if HSRP is active on any interface. If no HSRP configuration exists, this CVE does not apply.
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Check HSRP authentication configurationRun 'show standby interface <interface>' to inspect the HSRP configuration for the authentication setting. Look for 'Authentication' field.Affected if No MD5 authentication is configured (shows text-based authentication or no authentication).
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Inspect access controls on HSRP trafficRun 'show ip access-lists' and review any ACLs applied to interfaces or control plane for UDP port 1985. Also check 'show control-plane' for service policies.Affected if No ACL or control-plane filter blocks unauthorized traffic to UDP port 1985.
The device is affected if it runs Cisco IOS 12.1 with HSRP enabled on any interface and lacks MD5 authentication on HSRP plus access controls on UDP port 1985.
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 from the obsolete IOS 12.1 to a supported IOS version, enable HSRP MD5 authentication to prevent router spoofing, and implement access controls on UDP port 1985 (HSRP) to block unauthorized IRPAS traffic.
Fix this in iOS
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 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 $4,880.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2002-2053 — 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-2002-2053 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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