#VU23905 Use-after-return in TigerVNC - CVE-2019-15691

Vulnerability identifier: #VU23905

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-2019-15691

CWE-ID: CWE-672

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
TigerVNC
Web applications / Modules and components for CMS

Vendor: tigervnc.org

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to incorrect usage of stack memory in ZRLEDecoder. If decoding routine would throw an exception, ZRLEDecoder may try to access stack variable, which has been already freed during the process of stack unwinding. A remote attacker can execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

TigerVNC: 0.0.90 - 1.10.0

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External links
https://github.com/CendioOssman/tigervnc/commit/d61a767d6842b530ffb532ddd5a3d233119aad40
https://github.com/TigerVNC/tigervnc/releases/tag/v1.10.1
https://www.openwall.com/lists/oss-security/2019/12/20/2
https://ics-cert.kaspersky.com/advisories/klcert-advisories/2020/03/23/klcert-20-005-remote-code-execution-on-tigervnc-version-prior-to-1-10-1/

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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.