CVE-2007-3537
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 · uneditedIBM OS/400 (aka i5/OS) V4R2M0 through V5R3M0 on iSeries machines sends responses to TCP SYN-FIN packets, which allows remote attackers to obtain system information and possibly bypass firewall rules.
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 confidenceIBM OS/400 (i5/OS) versions V4R2M0 through V5R3M0 on iSeries systems improperly respond to TCP packets containing both SYN and FIN flags. This anomalous behavior allows remote attackers to elicit system responses and gather intelligence (such as open ports, OS fingerprints) that should not be disclosed, and potentially bypass firewalls that rely on filtering abnormal packet flag combinations.
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= r520= v4r2m0= v4r3= v4r4= v4r5= v5r1= v5r2m0= v5r3m0CVSS 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
- Complete
- Integrity
- None
- Availability
- None
AV:N/AC:L/Au:N/C:C/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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Identify the OS platformRun command 'DSPSYSVAL QSYSLIBL' or check system banner during IPL to confirm the operating system is IBM OS/400, i5/OS, or IBM iAffected if System is not running IBM OS/400 or i5/OS variant - not affected by this CVE
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Determine OS version numberExecute command 'DSPOBJD OBJ(QSYS/*ALL) OBJTYPE(*PGM) DETAIL(*VERSION)' or use 'WRKCFGSTS *NWS' to display the current OS version and release (V4R2M0 through V5R3M0)Affected if Unable to determine OS version - further investigation needed
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Compare installed version to affected rangeVerify the exact version string (e.g., V4R2M0, V4R3, V4R4, V4R5, V5R1, V5R2M0, or V5R3M0) against the known vulnerable versionsAffected if Installed version falls within V4R2M0 through V5R3M0 - system responds to SYN+FIN packets and is vulnerable to reconnaissance
A system is affected if it runs IBM OS/400 or i5/OS version V4R2M0 through V5R3M0, as these versions will respond to TCP packets with both SYN and FIN flags set.
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 dataPrimary remediation is to upgrade to a supported version of IBM i beyond V5R3M0. As an interim control, network firewalls can be configured to drop TCP packets with anomalous flag combinations (SYN-FIN, FIN-PSH-URG, etc.) before they reach affected systems.
- Consultation4.0 h
- Implementation16.0 h
- Testing8.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2007-3537 — 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-2007-3537 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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