An issue was discovered in OpenVPN 2.4.x before 2.4.9. 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.
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
| Link | Tags |
|---|---|
| https://github.com/OpenVPN/openvpn/commit/37bc691e7d26ea4eb61a8a434ebd7a9ae76225ab | third party advisory patch |
| https://security-tracker.debian.org/tracker/CVE-2020-11810 | third party advisory |
| https://bugzilla.suse.com/show_bug.cgi?id=1169925 | third party advisory issue tracking |
| https://community.openvpn.net/openvpn/ticket/1272 | vendor advisory exploit |
| https://patchwork.openvpn.net/patch/1079/ | patch vendor advisory |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FGHHV4YZANZW45KZTJJGVGPFMSXYRCKZ/ | vendor advisory |
| https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JII7RYYYRBPQNEGGVSOXCM7JUZ43T3VH/ | vendor advisory |
| https://lists.debian.org/debian-lts-announce/2022/05/msg00002.html | third party advisory mailing list |