CVE-2021-3908Network attack vector

Validator hang via unbounded certificate-chain traversal

Published Nov 11, 2021 · Updated Sep 16, 2024

Uncontrolled resource consumption in Cloudflare OctoRPKI before 1.4.0 allows remote attackers to hang the validator via RPKI input. Certificate-chain traversal accepts each attacker-controlled child CA without a depth bound, so validation never reaches a terminal node. Exploitation requires control of a CA in the configured trust chain, and the resulting infinite runtime interrupts route-origin validation.

CVSS severity5.9
Medium
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uncontrolled resource consumption in Cloudflare OctoRPKI before 1.4.0 allows remote attackers to hang the validator via RPKI input. Certificate-chain traversal accepts each attacker-controlled child CA without a depth bound, so validation never reaches a terminal node. Exploitation requires control of a CA in the configured trust chain, and the resulting infinite runtime interrupts route-origin validation.

The record

CVE
CVE-2021-3908
Published
Nov 11, 2021
Updated
Sep 16, 2024
Vendor
Cloudflare
Product
OctoRPKI
Classifications
CWE-400, CWE-835, T1499
Attack vector
network
Privileges
unauthenticated

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 privilegesunauthenticated

What is affected?

Cloudflare · OctoRPKIversion=unspecified <1.4.0

Published CVSS scores

5.9CloudflareCVSS:3.1/AV:N/AC:H/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.

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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-400Uncontrolled Resource Consumption
CWE-835Loop with Unreachable Exit Condition ('Infinite Loop')
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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