arch/i386/kernel/sysenter.c in the Virtual Dynamic Shared Objects (vDSO) implementation in the Linux kernel before 2.6.21 does not properly check boundaries, which allows local users to gain privileges or cause a denial of service via unspecified vectors, related to the install_special_mapping, syscall, and syscall32_nopage functions.
Debian Security Advisory 1687-1 - Several vulnerabilities have been discovered in the Linux kernel that may lead to a denial of service or privilege escalation.