Denial of service in OpenVPN



Risk Low
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2020-11810
CWE-ID CWE-399
Exploitation vector Network
Public exploit N/A
Vulnerable software
 OpenVPN for Windows
Client/Desktop applications / Software for system administration

Vendor OpenVPN

Security Bulletin

This security bulletin contains one low risk vulnerability.

1) Resource management error

EUVDB-ID: #VU27616

Risk: Low

CVSSv4.0: 1.7 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U/U:Clear]

CVE-ID: CVE-2020-11810

CWE-ID: CWE-399 - Resource Management Errors

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to improper management of internal resources within the application that allows a timing attack to be carried out against OpenVPN clients.

An attacker can inject a data channel v2 (P_DATA_V2) packet using a victim's peer-id. Normally such packets are dropped, but if this packet arrives before the data channel crypto parameters have been initialized, the victim's connection will be dropped. This requires careful timing due to the small time window (usually within a few seconds) between the victim client connection starting and the server PUSH_REPLY response back to the client. This attack will only work if Negotiable Cipher Parameters (NCP) is in use.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

OpenVPN for Windows: 2.4.0 - 2.4.8

CPE2.3 External links

https://bugzilla.suse.com/show_bug.cgi?id=1169925
https://community.openvpn.net/openvpn/ticket/1272
https://github.com/OpenVPN/openvpn/commit/37bc691e7d26ea4eb61a8a434ebd7a9ae76225ab
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FGHHV4YZANZW45KZTJJGVGPFMSXYRCKZ/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/JII7RYYYRBPQNEGGVSOXCM7JUZ43T3VH/
https://patchwork.openvpn.net/patch/1079/
https://security-tracker.debian.org/tracker/CVE-2020-11810


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.



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