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Ubuntu 20.04 LTS, USN-4434-1: LibVNCServer Denial of Service Risks

ubuntu
Calendar Grey July 23, 2020
Dist Ubuntu Esm H88
Several LibVNCServer vulnerabilities addressed in the Ubuntu security notification USN-4435-1 affecting various LTS versions.
Several security issues were fixed in LibVNCServer.

Summary

Several security issues were fixed in LibVNCServer.

Software Description:

- libvncserver: vnc server library

Details:

Ramin Farajpour Cami discovered that LibVNCServer incorrectly handled

certain malformed unix socket names. A remote attacker could exploit this

with a crafted socket name, leading to a denial of service, or possibly

execute arbitrary code. (CVE-2019-20839)

It was discovered that LibVNCServer did not properly access byte-aligned

data. A remote attacker could possibly use this issue to cause

LibVNCServer to crash, resulting in a denial of service. This issue only

affected Ubuntu 18.04 LTS and Ubuntu 16.04 LTS. (CVE-2019-20840)

Christian Beier discovered that LibVNCServer incorrectly handled anonymous

TLS connections. A remote attacker could possibly use this issue to cause

LibVNCServer to crash, resulting in a denial of service. This issue only

affected Ubuntu 20.04 LTS. (CVE-2020-14396)

It was discovered that LibVNCServer incorrectly hand...

Read the Full Advisory

Topics%20covered

Topics Covered

security advisory denial of service remote attack patch library issue ubuntu libvncserver

Update Instructions

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 20.04 LTS:
  libvncclient1                   0.9.12+dfsg-9ubuntu0.2
  libvncserver1                   0.9.12+dfsg-9ubuntu0.2

Ubuntu 18.04 LTS:
  libvncclient1                   0.9.11+dfsg-1ubuntu1.3
  libvncserver1                   0.9.11+dfsg-1ubuntu1.3

Ubuntu 16.04 LTS:
  libvncclient1                   0.9.10+dfsg-3ubuntu0.16.04.5
  libvncserver1                   0.9.10+dfsg-3ubuntu0.16.04.5

After a standard system update you need to restart LibVNCServer
applications to make all the necessary changes.

References

https://ubuntu.com/security/notices/USN-4434-1

CVE-2019-20839, CVE-2019-20840, CVE-2020-14396, CVE-2020-14397,

CVE-2020-14398, CVE-2020-14399, CVE-2020-14400, CVE-2020-14401,

CVE-2020-14402, CVE-2020-14403, CVE-2020-14404, CVE-2020-14405

Severity
critical
Lowest
Low
Medium
High
Critical

July 23, 2020

Topics%20covered

Topics Covered

security advisory denial of service remote attack patch library issue ubuntu libvncserver

Package Information

https://launchpad.net/ubuntu/+source/libvncserver/0.9.12+dfsg-9ubuntu0.2
https://launchpad.net/ubuntu/+source/libvncserver/0.9.11+dfsg-1ubuntu1.3
https://launchpad.net/ubuntu/+source/libvncserver/0.9.10+dfsg-3ubuntu0.16.04.5

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