CVE-2021-43172: Infinite length chain of RRDP repositories

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2021-11-09 · updated 2026-06-17
Weakness: CWE-674

Description

NLnet Labs Routinator prior to 0.10.2 happily processes a chain of RRDP repositories of infinite length causing it to never finish a validation run. In RPKI, a CA can choose the RRDP repository it wishes to publish its data in. By continuously generating a new child CA that only consists of another CA using a different RRDP repository, a malicious CA can create a chain of CAs of de-facto infinite length. Routinator prior to version 0.10.2 did not contain a limit on the length of such a chain and will therefore continue to process this chain forever. As a result, the validation run will never finish, 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.

Affected products

NLnet Labs Routinator: before 0.10.2 — fixed in 0.10.2

How to fix

Upgrade to a fixed version: NLnet Labs Routinator 0.10.2. Check the vendor advisory for mitigations.

References

Get alerted when CVE-2021-43172 or the next vulnerability affects your stack