CVE-2021-3909: Infinite open connection causes OctoRPKI to hang forever

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-11 · updated 2026-06-17
Weakness: CWE-400

Description

OctoRPKI does not limit the length of a connection, allowing for a slowloris DOS attack to take place which makes OctoRPKI wait forever. Specifically, the repository that OctoRPKI sends HTTP requests to will keep the connection open for a day before a response is returned, but does keep drip feeding new bytes to keep the connection alive.

Affected products

Cloudflare octorpki: before 1.3.0 — fixed in 1.3.0
Debian Linux: 11.0

How to fix

Upgrade to a fixed version: Cloudflare octorpki 1.3.0. Check the vendor advisory for mitigations.

References

https://github.com/cloudflare/cfrpki/security/advisories/GHSA-8cvr-4rrf-f244
https://www.debian.org/security/2021/dsa-5033
https://www.debian.org/security/2022/dsa-5041
https://github.com/cloudflare/cfrpki/security/advisories/GHSA-8cvr-4rrf-f244
https://www.debian.org/security/2021/dsa-5033
https://www.debian.org/security/2022/dsa-5041

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