4.3
CVSSv2

CVE-2020-11810

Published: 27/04/2020 Updated: 07/11/2023
CVSS v2 Base Score: 4.3 | Impact Score: 2.9 | Exploitability Score: 8.6
CVSS v3 Base Score: 3.7 | Impact Score: 1.4 | Exploitability Score: 2.2
VMScore: 383
Vector: AV:N/AC:M/Au:N/C:N/I:N/A:P

Vulnerability Summary

An issue exists in OpenVPN 2.4.x prior to 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.

Vulnerability Trend

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openvpn openvpn

debian debian linux 8.0

debian debian linux 9.0

debian debian linux 10.0

fedoraproject fedora 30

fedoraproject fedora 32

Vendor Advisories

This security issue is quite hard to abuse, requiring a fairly precise timing attack combined with guessing a just assigned peer-id reference If successful, only a single client just initiating a new connection will experience a denial of service situation(CVE-2020-11810) ...
A security issue has been found in OpenVPN before 249, where a 'peer-id' check is not performed correctly during a small amount of time after a connection has been established A rogue client sending a data channel packet during that time, from a different source address and with the same 'peer-id', would cause the client data to float to that ne ...