CVE-2021-3761: Cloudflare Octorpki

High severity, CVSS 7.5. EPSS: 1.2% chance of exploitation in the next 30 days.

Any CA issuer in the RPKI can trick OctoRPKI prior to 1.3.0 into emitting an invalid VRP "MaxLength" value, causing RTR sessions to terminate. An attacker can use this to disable RPKI Origin Validation in a victim network (for example AS 13335 - Cloudflare) prior to launching a BGP hijack which during normal operations would be rejected as "RPKI invalid". Additionally, in certain deployments RTR session flapping in and of itself also could cause BGP routing churn, causing availability issues.

Affected products

• Cloudflare Octorpki: before 1.3.0 (fixed in 1.3.0)
• Debian Debian Linux: version 11.0 only

Published 2021-09-09. Last modified 2026-06-17.