#VU27616 Resource management error in OpenVPN for Windows - CVE-2020-11810
Published: May 10, 2020
OpenVPN for Windows
OpenVPN
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.
Remediation
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