Use of Externally-Controlled Format String Affecting xen package, versions [,4.12.2)


Severity

Recommended
0.0
medium
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

EPSS
1.24% (86th percentile)

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  • Snyk IDSNYK-UNMANAGED-XEN-2384014
  • published26 Jan 2022
  • disclosed31 Oct 2019
  • creditUnknown

Introduced: 31 Oct 2019

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

How to fix?

Upgrade xen to version 4.12.2 or higher.

Overview

Affected versions of this package are vulnerable to Use of Externally-Controlled Format String. 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

CVSS Scores

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