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AUSCERT External Security Bulletin Redistribution
ESB-2020.2535
USN-4434-1: LibVNCServer vulnerabilities
24 July 2020
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AusCERT Security Bulletin Summary
---------------------------------
Product: LibVNCServer
Publisher: Ubuntu
Operating System: Ubuntu
Impact/Access: Execute Arbitrary Code/Commands -- Remote/Unauthenticated
Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2020-14405 CVE-2020-14404 CVE-2020-14403
CVE-2020-14402 CVE-2020-14401 CVE-2020-14400
CVE-2020-14399 CVE-2020-14398 CVE-2020-14397
CVE-2020-14396 CVE-2019-20840 CVE-2019-20839
Reference: ESB-2020.2469
ESB-2020.2248
Original Bulletin:
https://usn.ubuntu.com/4434-1/
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USN-4434-1: LibVNCServer vulnerabilities
23 July 2020
Several security issues were fixed in LibVNCServer.
Releases
o Ubuntu 20.04 LTS
o Ubuntu 18.04 LTS
o Ubuntu 16.04 LTS
Packages
o 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 handled region clipping. A
remote attacker could possibly use this issue to cause LibVNCServer to
crash, resulting in a denial of service. (CVE-2020-14397)
It was discovered that LibVNCServer did not properly reset incorrectly
terminated TCP connections. A remote attacker could possibly use this
issue to cause an infinite loop, resulting in a denial of service.
(CVE-2020-14398)
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. (CVE-2020-14399,
CVE-2020-14400)
It was discovered that LibVNCServer incorrectly handled screen scaling on
the server side. A remote attacker could use this issue to cause
LibVNCServer to crash, resulting in a denial of service, or possibly
execute arbitrary code. (CVE-2020-14401)
It was discovered that LibVNCServer incorrectly handled encodings. A
remote attacker could use this issue to cause LibVNCServer to crash,
resulting in a denial of service, or possibly execute arbitrary code.
(CVE-2020-14402, CVE-2020-14403, CVE-2020-14404)
It was discovered that LibVNCServer incorrectly handled TextChat messages.
A remote attacker could possibly use this issue to cause LibVNCServer to
crash, resulting in a denial of service. (CVE-2020-14405)
Update instructions
The problem can be corrected by updating your system to the following package
versions:
Ubuntu 20.04
o libvncclient1 - 0.9.12+dfsg-9ubuntu0.2
o libvncserver1 - 0.9.12+dfsg-9ubuntu0.2
Ubuntu 18.04
o libvncclient1 - 0.9.11+dfsg-1ubuntu1.3
o libvncserver1 - 0.9.11+dfsg-1ubuntu1.3
Ubuntu 16.04
o libvncclient1 - 0.9.10+dfsg-3ubuntu0.16.04.5
o 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
o CVE-2019-20839
o CVE-2019-20840
o CVE-2020-14396
o CVE-2020-14397
o CVE-2020-14398
o CVE-2020-14399
o CVE-2020-14400
o CVE-2020-14401
o CVE-2020-14402
o CVE-2020-14403
o CVE-2020-14404
o CVE-2020-14405
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