CVE-2021-43173

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. High risk of data tampering.

Exploit odds

1.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2021-11-09 17:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 1.4% in the next 30 days (EPSS).
• Severity: 7.5 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2021-11-09 17:15 UTC

Last modified

2026-06-17 04:10 UTC

Exploit probability

1.4% · EPSS, next 30 days

Weakness

CWE-755

Record status

Modified

Affected

• Nlnetlabs Routinator < 0.10.2
• Debian Linux 11.0

Attack profile CVSS 3.1 · 7.5

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-43173.md and follow it. Check whether this project is affected by CVE-2021-43173. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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