CVE-2021-41531Network attack vector

Route Origin Validation disablement via unchecked ROA max-length

Published Sep 21, 2021 · Updated Sep 16, 2024

Improper ROA validation in NLnet Labs Routinator 0.9.0 and earlier allows remote attackers to disable Route Origin Validation. Routinator passes an RPKI CA's max-length value through to its RTR payload without checking that it does not exceed the address family's maximum prefix length. A CA able to publish such a ROA can cause RTR clients to reject the entire data set, leaving downstream routers without Route Origin Validation.

CVSS severity7.5
High
EPSS probability0.93%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper ROA validation in NLnet Labs Routinator 0.9.0 and earlier allows remote attackers to disable Route Origin Validation. Routinator passes an RPKI CA's max-length value through to its RTR payload without checking that it does not exceed the address family's maximum prefix length. A CA able to publish such a ROA can cause RTR clients to reject the entire data set, leaving downstream routers without Route Origin Validation.

The record

CVE
CVE-2021-41531
Published
Sep 21, 2021
Updated
Sep 16, 2024
Vendor
NLnet Labs
Product
Routinator
Classifications
CWE-20, CWE-1288, T1562
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 21, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <=0.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

NLnet Labs · Routinatorversion=unspecified <=0.9.0

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:P/A:N
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-1288Improper Validation of Consistency within Input
T1562Impair Defenses

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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