#VU30157 Out-of-bounds write in LibVNCServer - CVE-2017-18922

Vulnerability identifier: #VU30157

Vulnerability risk: High

CVSSv4.0: 8.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Amber]

CVE-ID: CVE-2017-18922

CWE-ID: CWE-787

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
LibVNCServer
Server applications / Remote management servers, RDP, SSH

Vendor: LibVNC

Description

The vulnerability allows a remote non-authenticated attacker to execute arbitrary code.

It was discovered that websockets.c in LibVNCServer prior to 0.9.12 did not properly decode certain WebSocket frames. A malicious attacker could exploit this by sending specially crafted WebSocket frames to a server, causing a heap-based buffer overflow.

Mitigation
Install update from vendor's website.

Vulnerable software versions

LibVNCServer: 0.9.0 - 0.9.11

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External links
https://lists.opensuse.org/opensuse-security-announce/2020-07/msg00020.html
https://www.openwall.com/lists/oss-security/2020/06/30/3
https://bugzilla.redhat.com/show_bug.cgi?id=1852356
https://github.com/LibVNC/libvncserver/commit/aac95a9dcf4bbba87b76c72706c3221a842ca433
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/4F6FUH4EFK4NAP6GT4TQRTBKWIRCZLIY/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NVP7TJVYJDXDFRHVQ3ENEN3H354QPXEZ/
https://usn.ubuntu.com/4407-1/
https://www.openwall.com/lists/oss-security/2020/06/30/2

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.