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Vulnerability of QEMU: denial of service via VirtFS Directory Sharing

Synthesis of the vulnerability 

An attacker, inside a guest system, can trigger a fatal error via VirtFS Directory Sharing of QEMU, in order to trigger a denial of service on the host system.
Impacted products: Debian, QEMU, SLES, Ubuntu.
Severity of this bulletin: 1/4.
Creation date: 08/02/2021.
Références of this threat: CVE-2021-20181, DLA-2560-1, SUSE-SU-2021:0521-1, USN-4725-1, VIGILANCE-VUL-34509, ZDI-21-159.

Description of the vulnerability 

An attacker, inside a guest system, can trigger a fatal error via VirtFS Directory Sharing of QEMU, in order to trigger a denial of service on the host system.
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This cybersecurity alert impacts software or systems such as Debian, QEMU, SLES, Ubuntu.

Our Vigil@nce team determined that the severity of this weakness is low.

The trust level is of type confirmed by the editor, with an origin of user shell.

An attacker with a expert ability can exploit this security weakness.

Solutions for this threat 

QEMU: patch for VirtFS Directory Sharing.
A patch is indicated in information sources.

Debian 9: new qemu packages.
New packages are available:
  Debian 9: qemu 1:2.8+dfsg-6+deb9u13

SUSE LE 15 SP2: new qemu packages.
New packages are available:
  SUSE LE 15 SP2: qemu 4.2.1-11.13.1

Ubuntu: new qemu packages.
New packages are available:
  Ubuntu 20.10: qemu 1:5.0-5ubuntu9.4
  Ubuntu 20.04 LTS: qemu 1:4.2-3ubuntu6.12
  Ubuntu 18.04 LTS: qemu 1:2.11+dfsg-1ubuntu7.35
  Ubuntu 16.04 LTS: qemu 1:2.5+dfsg-5ubuntu10.49
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