12000 RouterHardware / appliance · Cisco
CVE-2001-0867
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 · uneditedCisco 12000 with IOS 12.0 and line cards based on Engine 2 does not properly filter does not properly filter packet fragments even when the "fragment" keyword is used in an ACL, which allows remote attackers to bypass the intended access controls.
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 12000 series routers running IOS 12.0 with Engine 2-based line cards fail to properly filter IP packet fragments when the 'fragment' keyword is configured in access control lists. This allows remote attackers to bypass intended ACL restrictions by transmitting malicious traffic as fragmented packets that bypass the incomplete fragment filtering.
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
12000 RouterHardware / 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
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:L/Au:N/C:P/I:P/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 modelExecute 'show version' or check hardware inventory to confirm the device is a Cisco 12000 series routerAffected if The device is not a Cisco 12000 series router, then this CVE does not apply
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Check the IOS versionExecute 'show version' and look for 'IOS (tm) 12.0' in the displayed software version informationAffected if IOS version is 12.0 (any subversion) - other major versions may have different behavior
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Identify line card engine typeExecute 'show diag' or 'show hardware' to list installed line cards and their engine types; look for 'Engine 2' or '2' in the line card descriptionAffected if Engine 2-based line cards are present - this is required for the vulnerability to manifest
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Locate ACLs using the fragment keywordExecute 'show ip access-lists' and review each ACL for entries containing the 'fragment' keywordAffected if ACL entries with the 'fragment' keyword are configured - these entries may not filter properly on Engine 2 line cards
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Verify fragment filtering behaviorSend fragmented test packets (non-initial fragments) matching an ACL with 'fragment' keyword and observe whether they bypass the filter; compare with 'show access-lists' fragment counters if availableAffected if Fragmented packets matching 'fragment' keyword ACL entries pass through when they should be denied, indicating incomplete filtering
The environment is affected if it consists of a Cisco 12000 router running IOS 12.0 with Engine 2-based line cards that have ACLs configured with the 'fragment' keyword.
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 IOS to a version that properly handles fragment filtering on Engine 2 line cards, or implement alternative filtering mechanisms such as IP fragmentation handling at other network layers.
Fix this in 12000 Router
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 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 $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2001-0867 — 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-2001-0867 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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