Use of Externally-Controlled Format String Affecting xen-devel package, versions <4.10.4_06-3.25.1


Severity

Recommended
high

Based on SUSE Linux Enterprise Server security rating.

Threat Intelligence

EPSS
1.15% (86th percentile)

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  • Snyk IDSNYK-SLES150-XENDEVEL-2725356
  • published14 Apr 2022
  • disclosed12 Nov 2019

Introduced: 12 Nov 2019

CVE-2019-18420  (opens in a new tab)
CWE-134  (opens in a new tab)

How to fix?

Upgrade SLES:15.0 xen-devel to version 4.10.4_06-3.25.1 or higher.

NVD Description

Note: Versions mentioned in the description apply only to the upstream xen-devel package and not the xen-devel package as distributed by SLES. See How to fix? for SLES:15.0 relevant fixed versions and status.

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.

CVSS Scores

version 3.1