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Vulnerability record · CVE-2021-43173 · published 9 November 2021

CVE-2021-43173: Nlnetlabs routinator uncontrolled resource consumption vulnerability

Nlnetlabs · Routinator

In NLnet Labs Routinator prior to 0.10.2, a validation run can be delayed significantly by an RRDP repository by not answering but slowly drip-feeding bytes to keep the connection alive. This can be used to effectively stall validation. While Routinator has a configurable time-out value for RRDP connections, this time-out was only applied to individual read or write operations rather than the complete request. Thus, if an RRDP repository sends a little bit of data before that time-out expired, it can continuously extend the time it takes for the request to finish. Since validation will only continue once the update of an RRDP repository has concluded, this delay will cause validation to stall, leading to Routinator continuing to serve the old data set or, if in the initial validation run directly after starting, never serve any data at all.

7.5 CVSS 3.1 High EPSS 1.5% · top 27.1% CWE-755 · CWE-755CWE-400 · Uncontrolled resource consumption
7.5CVSS 3.1 base score, v2 5.0
1.5%EPSS exploitation probability, 30 days
NoNot in CISA KEV
2Affected product versions listed by NVD
6References
17 Jun 2026Last modified by NVD

Description

In NLnet Labs Routinator prior to 0.10.2, a validation run can be delayed significantly by an RRDP repository by not answering but slowly drip-feeding bytes to keep the connection alive. This can be used to effectively stall validation. While Routinator has a configurable time-out value for RRDP connections, this time-out was only applied to individual read or write operations rather than the complete request. Thus, if an RRDP repository sends a little bit of data before that time-out expired, it can continuously extend the time it takes for the request to finish. Since validation will only continue once the update of an RRDP repository has concluded, this delay will cause validation to stall, leading to Routinator continuing to serve the old data set or, if in the initial validation run directly after starting, never serve any data at all.

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

Affected products

2 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://www.debian.org/security/2021/dsa-5033 Third Party Advisory
https://www.debian.org/security/2022/dsa-5041 Third Party Advisory
https://www.nlnetlabs.nl/downloads/routinator/CVE-2021-43172_CVE-2021-43173_CVE-2021-43174.txt Vendor Advisory
https://www.debian.org/security/2021/dsa-5033 Third Party Advisory
https://www.debian.org/security/2022/dsa-5041 Third Party Advisory
https://www.nlnetlabs.nl/downloads/routinator/CVE-2021-43172_CVE-2021-43173_CVE-2021-43174.txt Vendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-43173), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.