CVE-2021-3909

Name: CVE-2021-3909
Creator: NVD / NIST
Published: 2021-11-11T22:15:07.923+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.51%

Last modified Jun 17, 2026

CVE-2021-3909 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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.. EPSS estimates a 1.51% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

1.51%

71.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Cloudflare	Octorpki	< 1.3.0
Debian	Debian Linux	11.0

References

https://github.com/cloudflare/cfrpki/security/advisories/GHSA-8cvr-4rrf-f244Third Party Advisory
https://www.debian.org/security/2021/dsa-5033Third Party Advisory
https://www.debian.org/security/2022/dsa-5041Third Party Advisory
https://github.com/cloudflare/cfrpki/security/advisories/GHSA-8cvr-4rrf-f244Third Party Advisory
https://www.debian.org/security/2021/dsa-5033Third Party Advisory
https://www.debian.org/security/2022/dsa-5041Third Party Advisory

Timeline

Published: Nov 11, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-3909?

How severe is CVE-2021-3909?

CVE-2021-3909 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.51% probability of exploitation in the next 30 days.

How do I fix CVE-2021-3909?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-3909?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST