ID CVE-2019-18420
Summary An issue was discovered in Xen through 4.12.x allowing x86 PV guest OS users to cause a denial of service via a VCPUOP_initialise hypercall. hypercall_create_continuation() is a variadic function which uses a printf-like format string to interpret its parameters. Error handling for a bad format character was done using BUG(), which crashes Xen. One path, via the VCPUOP_initialise hypercall, has a bad format character. The BUG() can be hit if VCPUOP_initialise executes for a sufficiently long period of time for a continuation to be created. Malicious guests may cause a hypervisor crash, resulting in a Denial of Service (DoS). Xen versions 4.6 and newer are vulnerable. Xen versions 4.5 and earlier are not vulnerable. Only x86 PV guests can exploit the vulnerability. HVM and PVH guests, and guests on ARM systems, cannot exploit the vulnerability.
References
Vulnerable Configurations
  • cpe:2.3:o:xen:xen:4.8.0:*:*:*:*:*:x86:*
    cpe:2.3:o:xen:xen:4.8.0:*:*:*:*:*:x86:*
CVSS
Base: 6.3 (as of 24-08-2020 - 17:37)
Impact:
Exploitability:
CWE CWE-134
CAPEC
  • String Format Overflow in syslog()
    This attack targets the format string vulnerabilities in the syslog() function. An attacker would typically inject malicious input in the format string parameter of the syslog function. This is a common problem, and many public vulnerabilities and associated exploits have been posted.
  • Format String Injection
    An adversary includes formatting characters in a string input field on the target application. Most applications assume that users will provide static text and may respond unpredictably to the presence of formatting character. For example, in certain functions of the C programming languages such as printf, the formatting character %s will print the contents of a memory location expecting this location to identify a string and the formatting character %n prints the number of DWORD written in the memory. An adversary can use this to read or write to memory locations or files, or simply to manipulate the value of the resulting text in unexpected ways. Reading or writing memory may result in program crashes and writing memory could result in the execution of arbitrary code if the adversary can write to the program stack.
Access
VectorComplexityAuthentication
NETWORK MEDIUM SINGLE
Impact
ConfidentialityIntegrityAvailability
NONE NONE COMPLETE
cvss-vector via4 AV:N/AC:M/Au:S/C:N/I:N/A:C
refmap via4
bugtraq 20200114 [SECURITY] [DSA 4602-1] xen security update
debian DSA-4602
fedora
  • FEDORA-2019-376ec5c107
  • FEDORA-2019-865bb16900
  • FEDORA-2019-cbb732f760
gentoo GLSA-202003-56
misc http://xenbits.xen.org/xsa/advisory-296.html
mlist [oss-security] 20191031 Xen Security Advisory 296 v4 (CVE-2019-18420) - VCPUOP_initialise DoS
suse openSUSE-SU-2019:2506
Last major update 24-08-2020 - 17:37
Published 31-10-2019 - 14:15
Last modified 24-08-2020 - 17:37
Back to Top