CVE intelligence and bounded remediation

CVE-2020-11810 — An issue was discovered in OpenVPN 2.4.x before 2.4.9

Medium CVSS 4.3

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.

Severity
Medium
CVSS
4.3 (2.0)
Published
2020-04-27
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-362

Affected products

  • openvpn / openvpn
  • debian / debian_linux / 8.0
  • debian / debian_linux / 9.0
  • debian / debian_linux / 10.0
  • fedoraproject / fedora / 30
  • fedoraproject / fedora / 32

Matched remediation archetype

Race condition, TOCTOU, and lifecycle synchronization

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Check exposure

  • Map concurrent actors, shared state, lock boundaries, signals, callbacks, retries, and check-then-use sequences in the affected path.
  • Determine whether untrusted users can influence timing, object names, filesystem state, or repeated state transitions.
  • Identify clustered and multi-process behavior that repository-local tests may not represent.

Remediate safely

  • Make the sensitive state transition atomic or protect it with a consistently ordered synchronization primitive.
  • Perform authorization and invariant checks on the same authoritative object and transaction used for the operation.
  • Use unique private resources, safe ownership transfer, and idempotent operations; add deterministic concurrency regression tests.

Authoritative sources

Complete CVE record and remediation plan

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