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Reference: CERT-EU Security Advisory 2012-0077
 
Title: Linux kernel security flaw in the NFSv4 implementation [1]
 
Version history:
21.06.2012 Initial publication

Summary
=======
The NFSv4 implementation in the Linux kernel before 3.2.2 does not properly handle bitmap sizes in 
GETACL replies, which allows remote NFS servers to cause a denial of service (OOPS) by sending an 
excessive number of bitmap words. [1,2,6,7]
 

CVE-2011-4131
CVSS v2 Base Score:4.6 (MEDIUM) (AV:A/AC:H/Au:N/C:N/I:N/A:C)  [4,5]

Vulnerable systems
==================
Linux kernel before 3.2.2

Original Details
================
A flaw was found in the way the Linux kernel's Event Poll (epoll) subsystem handled large, nested 
epoll structures. A local, unprivileged user could use this flaw to cause a denial of service. [2]

A remote NFS server (attacker) could exploit this flaw to cause a denial of service.[7]

A malicious Network File System version 4 (NFSv4) server could return a crafted reply to a GETACL 
request, causing a denial of service on the client. [2]

What can you do?
================
Fix is available via some vendors [3,6,7]

What to tell your users?
========================
N/A

More information
================

[1] https://access.redhat.com/security/cve/CVE-2011-4131
[2] https://rhn.redhat.com/errata/RHSA-2012-0862.html
[3] https://access.redhat.com/knowledge/articles/11258
[4] http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2011-4131
[5] More information about CVSS is available at: http://www.first.org/cvss/cvss-guide.html
[6] http://security-tracker.debian.org/tracker/CVE-2011-4131
[7] http://people.canonical.com/~ubuntu-security/cve/2011/CVE-2011-4131.html

Best regards,

CERT-EU Pre-configuration Team (http://cert.europa.eu)
Phone: +32.2.2990005 / e-mail: cert-eu@ec.europa.eu
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