An issue was discovered in LibVNCServer before 0.9.13. libvncclient/tls_openssl.c has a NULL pointer dereference.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - An issue was discovered in LibVNCServer before 0.9.13. libvncclient/tls_openssl.c has a NULL pointer     dereference. (CVE-2020-14396)

Note that Nessus relies on the presence of the package as reported by the vendor.

The remote Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS host has packages installed that are affected by multiple vulnerabilities as referenced in the USN-4434-1 advisory.

    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)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Type	Severity
257258	Linux Distros Unpatched Vulnerability : CVE-2020-14396	Nessus	Misc.	Local	high
138999	Ubuntu 16.04 LTS / 18.04 LTS / 20.04 LTS : LibVNCServer vulnerabilities (USN-4434-1)	Nessus	Ubuntu Local Security Checks	Local	medium

Detections

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CVE-2020-14396

high

Tenable Plugins

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medium