The (1) do_send and (2) do_recv functions in io.c in libvchan in Xen 4.2.x, 4.3.x, and 4.4-RC series allows local guests to cause a denial of service or possibly gain privileges via crafted xenstore ring indexes, which triggers a "read or write past the end of the ring."

References

• https://nvd.nist.gov/vuln/detail/CVE-2014-1896
• http://lists.opensuse.org/opensuse-security-announce/2014-03/msg00011.html
• http://security.gentoo.org/glsa/glsa-201407-03.xml
• http://www.openwall.com/lists/oss-security/2014/02/07/12
• http://www.openwall.com/lists/oss-security/2014/02/10/7
• http://xenbits.xen.org/xsa/advisory-86.html
• http://xenbits.xen.org/xsa/xsa86.patch