CVE-2021-3911Network attack vector

Validator crash via oversized ROA address field

Published Nov 11, 2021 · Updated Sep 16, 2024

Improper input validation in Cloudflare OctoRPKI before 1.4.0 allows remote attackers controlling an RPKI repository to crash the validator. The ROA parser accepts an IP address bit string longer than its address family permits and reaches unchecked bounds during validation. Exploitation requires the crafted ROA to be ingested during a validation refresh, terminating the process and interrupting route-origin validation.

CVSS severity4.2
Medium
EPSS probability0.91%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in Cloudflare OctoRPKI before 1.4.0 allows remote attackers controlling an RPKI repository to crash the validator. The ROA parser accepts an IP address bit string longer than its address family permits and reaches unchecked bounds during validation. Exploitation requires the crafted ROA to be ingested during a validation refresh, terminating the process and interrupting route-origin validation.

The record

CVE
CVE-2021-3911
Published
Nov 11, 2021
Updated
Sep 16, 2024
Vendor
Cloudflare
Product
OctoRPKI
Classifications
CWE-20, CWE-252, T1499.004
Attack vector
network
Privileges
admin

Timeline

How it unfolded

  1. Nov 11, 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 <1.4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesadmin

What is affected?

Cloudflare · OctoRPKIversion=unspecified <1.4.0

Published CVSS scores

4.2Cloudflare, Inc.CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H
4.3NIST National Vulnerability DatabaseAV:N/AC:M/Au:N/C:N/I:N/A:P
6.5NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-252Unchecked Return Value
T1499.004Application or System Exploitation

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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