CVE-2021-3761Network attack vector

RTR session termination via unchecked ROA maxLength

Published Sep 9, 2021 · Updated Sep 17, 2024

ROA validation in Cloudflare OctoRPKI before 1.3.0 allows remote attackers to terminate RTR sessions via a crafted maxLength value. ROAEntry.Validate accepts maxLength values above 32 for IPv4 or 128 for IPv6, allowing invalid VRPs into generated output. An attacker must control an RPKI CA issuer; repeated RTR termination can disable origin validation or cause routing churn, but does not directly alter routes.

CVSS severity7.5
High
EPSS probability1.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

ROA validation in Cloudflare OctoRPKI before 1.3.0 allows remote attackers to terminate RTR sessions via a crafted maxLength value. ROAEntry.Validate accepts maxLength values above 32 for IPv4 or 128 for IPv6, allowing invalid VRPs into generated output. An attacker must control an RPKI CA issuer; repeated RTR termination can disable origin validation or cause routing churn, but does not directly alter routes.

The record

CVE
CVE-2021-3761
Published
Sep 9, 2021
Updated
Sep 17, 2024
Vendor
Cloudflare
Product
OctoRPKI
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 9, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=unspecified <1.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloudflare · OctoRPKIversion=unspecified <1.3.0

Published CVSS scores

5.0NIST National Vulnerability DatabaseAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5CloudflareCVSS:3.1/AV:N/AC:L/PR:N/UI:N/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
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

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo