Broadband Operating SystemOperating system · Cisco
CVE-2001-0055
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 · uneditedCBOS 2.4.1 and earlier in Cisco 600 routers allows remote attackers to cause a denial of service via a slow stream of TCP SYN packets.
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 Cisco 600 router running CBOS 2.4.1 and earlier contains a denial-of-service vulnerability where slow-rate TCP SYN packet streams exhaust device resources, preventing legitimate connections.
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
Broadband Operating SystemOperating system
<= 2.3.8
Cisco 6xx RoutersHardware / appliance
all versionsCVSS 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 router modelDetermine if the device is a Cisco 600 series or 6xx router by checking the hardware label, SNMP sysDescr, or console output during startupAffected if The device is a Cisco 600 series or any Cisco 6xx router model
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Check the CBOS versionAccess the router console or management interface and run 'show version' or similar command to display the running CBOS firmware versionAffected if The CBOS version is 2.4.1 or earlier, or specifically 2.3.8 or below for the CBOS product range
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Verify if rate limiting is configuredCheck the router configuration for any rate-limiting, traffic policing, or access control entries designed to limit TCP SYN packet ratesAffected if No SYN flood mitigation or rate limiting is configured on the device
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Assess network exposureDetermine whether the router WAN or LAN interfaces are directly exposed to untrusted TCP traffic from the internet or untrusted networksAffected if The router accepts TCP connections from untrusted or internet-facing networks without upstream filtering
A user is affected if they are running a Cisco 600/6xx router with CBOS version 2.4.1 or earlier, and the device is exposed to untrusted TCP traffic without SYN flood mitigation configured.
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 CBOS to a version newer than 2.4.1, or replace the legacy Cisco 600 router with modern hardware. Implement network-level rate limiting or firewall filters to block SYN flood traffic.
Fix this in Broadband Operating System
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2001-0055 — 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-2001-0055 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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