dbcve.org
Linux KernelOperating system · Linux

CVE-2009-3726

HIGH · 7.8 CVSS v2.0 Published 2009-11-09
Fix available
A fix is available. Upgrade to after 2.6.31 or later.
See remediation →
87/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
The nfs4_proc_lock function in fs/nfs/nfs4proc.c in the NFSv4 client in the Linux kernel before 2.6.31-rc4 allows remote NFS servers to cause a denial of service (NULL pointer dereference and panic) by sending a certain response containing incorrect file attributes, which trigger attempted use of an open file that lacks NFSv4 state.

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 confidence

The NFSv4 client in Linux kernel before 2.6.31-rc4 contains a NULL pointer dereference in the nfs4_proc_lock function. A malicious or misconfigured remote NFS server can send a response with incorrect file attributes, causing the client to attempt access to an open file lacking NFSv4 state, resulting in kernel panic and denial of service.

MitigationUpgrade the Linux kernel to version 2.6.31-rc4 or later to patch the vulnerability. If immediate upgrade is not feasible, consider network-level controls to restrict NFS access to trusted servers.

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
Affected:<= 2.6.31= 2.2.27= 2.4.1= 2.4.2= 2.4.3= 2.4.4= 2.4.5= 2.4.6= 2.4.7= 2.4.8= 2.4.9= 2.4.10

CVSS 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
Complete

AV:N/AC:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Check kernel version
    Run 'uname -r' to get the running kernel version and compare it to the affected ranges (2.6.31 and below, or specific 2.2.x/2.4.x versions listed in the CVE)
    Affected if The kernel version is 2.6.31 or earlier, or matches any of the specific 2.2.x/2.4.x versions listed (2.2.27, 2.4.1-2.4.10)
  2. Identify NFSv4 client usage
    Run 'mount -t nfs4' to list currently mounted NFSv4 shares, or check /proc/mounts for 'nfs4' mount types
    Affected if Any NFSv4 mounts are active on the system
  3. Verify NFS client configuration
    Check /etc/fstab or use 'mount' command to identify any NFS mounts that could use NFSv4 protocol (look for 'vers=4' or nfs4 mount type)
    Affected if The system is configured to mount NFS shares using NFSv4 protocol
  4. Check for NFSv4 kernel module
    Run 'lsmod | grep nfs' to see if NFS modules are loaded, or check /proc/filesystems for nfs4 support
    Affected if NFSv4 client support is compiled and loaded on the system

The system is vulnerable if it runs an affected kernel version AND has NFSv4 client functionality enabled or configured to connect to potentially untrusted NFS servers.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Upgrade available Upgrade to a release after 2.6.31
Interim mitigation

Upgrade the Linux kernel to version 2.6.31-rc4 or later to patch the vulnerability. If immediate upgrade is not feasible, consider network-level controls to restrict NFS access to trusted servers.

Fix this in Linux Kernel Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,272.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2009-3726 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2009-3726 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

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.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data