Linux KernelOperating system · Linux
CVE-2003-0187
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 connection tracking core of Netfilter for Linux 2.4.20, with CONFIG_IP_NF_CONNTRACK enabled or the ip_conntrack module loaded, allows remote attackers to cause a denial of service (resource consumption) due to an inconsistency with Linux 2.4.20's support of linked lists, which causes Netfilter to fail to identify connections with an UNCONFIRMED status and use large timeouts.
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 confidenceNetfilter connection tracking (ip_conntrack) in Linux kernel 2.4.20 fails to properly handle UNCONFIRMED connections due to a linked list implementation inconsistency, causing these connections to use abnormally large timeouts and accumulate, leading to resource exhaustion (memory/connection table saturation).
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
Linux KernelOperating system
= 2.4.20CVSS 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 running kernel versionRun `uname -r` or check `/proc/version` to obtain the exact kernel versionAffected if The version is exactly 2.4.20 (only this specific version is affected)
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Verify if connection tracking is enabledCheck if CONFIG_IP_NF_CONNTRACK is set in the kernel configuration (typically in /boot/config-`uname -r` or /proc/config.gz) or if the ip_conntrack module is loaded (run `lsmod | grep ip_conntrack` or check /proc/net/ip_conntrack)Affected if Connection tracking module is loaded or the kernel has CONFIG_IP_NF_CONNTRACK enabled (the flaw requires this feature to be present)
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Inspect connection tracking table for anomaliesExamine /proc/net/ip_conntrack for a large number of UNCONFIRMED connections, or use `conntrack -L` if the tool is available, looking for entries in UNCONFIRMED stateAffected if The connection tracking table shows an abnormally large number of UNCONFIRMED entries or the table appears saturated
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Monitor memory and connection tracking resourcesCheck kernel memory pressure via `free -m`, `vmstat 1`, or looking at /proc/meminfo, and observe if connection tracking is consuming excessive memory or if the conntrack table has reached its limitsAffected if System memory is being exhausted by connection tracking entries, or the conntrack table hash buckets show unusual growth
You are affected if your system runs exactly Linux kernel 2.4.20 AND has connection tracking (ip_conntrack) enabled, and you observe accumulation of UNCONFIRMED connections or resource exhaustion from the connection tracking 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 dataUpgrade Linux kernel to version 2.4.21 or later which contains the fixed linked list handling, or disable CONFIG_IP_NF_CONNTRACK if upgrade is not feasible.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2003-0187 — 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-2003-0187 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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