kernel is vulnerable to denial of service. It was found that a malicious guest running on the Xen hypervisor could place invalid data in the memory that the guest shared with the blkback and blktap back-end drivers, resulting in a denial of service on the host system.
docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5/html/5.5_Technical_Notes/kernel.html#RHSA-2011-0004
secunia.com/advisories/35093
secunia.com/advisories/42789
secunia.com/advisories/46397
www.openwall.com/lists/oss-security/2010/11/23/1
www.openwall.com/lists/oss-security/2010/11/24/8
www.redhat.com/support/errata/RHSA-2011-0004.html
www.securityfocus.com/archive/1/520102/100/0/threaded
www.securityfocus.com/bid/45029
www.vmware.com/security/advisories/VMSA-2011-0012.html
www.vupen.com/english/advisories/2011/0024
xenbits.xensource.com/linux-2.6.18-xen.hg?rev/7070d34f251c
xenbits.xensource.com/linux-2.6.18-xen.hg?rev/77f831cbb91d
access.redhat.com/errata/RHSA-2011:0004
access.redhat.com/security/updates/classification/#important
bugzilla.redhat.com/show_bug.cgi?id=656206