Linux KernelOperating system · Linux
CVE-2009-4308
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 ext4_decode_error function in fs/ext4/super.c in the ext4 filesystem in the Linux kernel before 2.6.32 allows user-assisted remote attackers to cause a denial of service (NULL pointer dereference), and possibly have unspecified other impact, via a crafted read-only filesystem that lacks a journal.
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 confidenceThe ext4_decode_error function in fs/ext4/super.c in the Linux kernel before 2.6.32 contains a NULL pointer dereference vulnerability when processing a crafted read-only ext4 filesystem that lacks a journal. An attacker must trick a user into mounting the malicious filesystem to trigger the 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
Linux KernelOperating system
<= 2.6.31= 2.6.0= 2.6.1= 2.6.2= 2.6.3= 2.6.4= 2.6.5= 2.6.6= 2.6.7= 2.6.8= 2.6.8.1= 2.6.9CVSS 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
- M
- Authentication
- None
- Confidentiality
- None
- Integrity
- None
- Availability
- Complete
AV:N/AC:M/Au:N/C:N/I:N/A:C
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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Check the running kernel versionRun `uname -r` or `cat /proc/version` to obtain the kernel versionAffected if The version is 2.6.31 or earlier, or matches any of the affected versions (2.6.0 through 2.6.9)
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Verify ext4 filesystem support is enabledCheck if the ext4 module is loaded (`lsmod | grep ext4`) or if ext4 is built into the kernel (check kernel config or `/boot/config-$(uname -r)` for CONFIG_EXT4_FS)Affected if ext4 support is present in the kernel (module or built-in)
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Identify mounted ext4 filesystemsRun `mount | grep -i ext4` or `df -T | grep ext4` to list any ext4 filesystems currently mountedAffected if Any ext4 filesystems are mounted, especially read-only ones without a journal (though journal status is not easily visible at runtime)
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Check for journal presence on mounted ext4 filesystemsRun `tune2fs -l /dev/<device> | grep -i journal` for each ext4 mount to check for journal presenceAffected if Any ext4 filesystem is mounted that lacks a journal (this is the specific condition that enables the vulnerability)
You are affected if your kernel version is 2.6.31 or earlier AND ext4 support is enabled, particularly if you may mount untrusted read-only ext4 filesystems without a journal.
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 the Linux kernel to version 2.6.32 or later. Avoid mounting untrusted or unknown ext4 filesystems, especially read-only ones, until the kernel is patched.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation4.0 h
- Implementation4.0 h
- Testing6.0 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 $4,448.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2009-4308 — 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-2009-4308 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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