How severe is CVE-2021-3908?

CVE-2021-3908 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-3908?

CVE-2021-3908 affects the following packages: github.com/cloudflare/cfrpki (Go). Ecosystems affected: Go.

How do I fix CVE-2021-3908?

Update github.com/cloudflare/cfrpki to 1.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3908 is resolved across your whole dependency graph.

How do I detect CVE-2021-3908 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cloudflare/cfrpki, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-3908 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2021-3908 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-3908 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-3908?

CVE-2021-3908 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 54th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2021-3908?

CVE-2021-3908 is classified as Uncontrolled Resource Consumption (CWE-400), CWE-835 (CWE-835). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-3908 published, and has it been updated?

CVE-2021-3908 was published on November 11, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹

🐹 Go

Not in CISA KEV

HIGH severity

CVE-2021-3908 — cfrpki

HIGH

CVE-2021-3908 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in github.com/cloudflare/cfrpki. A fix is available for github.com/cloudflare/cfrpki — see the affected versions and patch details below.

Infinite certificate chain depth results in OctoRPKI running forever

Also known asGHSA-g5gj-9ggf-9vmqGO-2022-0249

Published

Nov 11, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 1, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐹github.com/cloudflare/cfrpki

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

For more information

If you have any questions or comments about this advisory email us at [email protected]

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/cloudflare/cfrpki`	all versions	1.4.0`go get github.com/cloudflare/cfrpki@v1.4.0`

Affected Products

2 products · 2 configurations

Application

octorpkicloudflare

< 1.3.0

range

debian linuxdebian

1 version

11.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/cloudflare/cfrpki, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/cloudflare/cfrpki to 1.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-3908 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

OctoRPKI (github.com/cloudflare/cfrpki/cmd/octorpki) does not limit the depth of a certificate chain, allowing for a CA to create children in an ad-hoc fashion, thereby making tree traversal never end. ### For more information If you have any questions or comments about this advisory email us at [email protected]

O3 Security · Impact-Aware SCA

Is CVE-2021-3908 in your dependencies?

Find it across Go, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

7.5/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CWE Classification

CWE-400Uncontrolled Resource Consumption CWE-835CWE-835

Weaponization

No Nuclei template, Metasploit module or public proof-of-concept found.

OpenSSF Scorecard

Package health score

cfrpki

4.7/10

Code-Review7/10

Maintained0/10

Branch-ProtectionN/A

Assessed Oct 26, 2026

Timeline

Disclosed

Nov 11, 2021

Last updated

Oct 20, 2026

Identifiers

CVE-2021-3908

GHSA-g5gj-9ggf-9vmq

GO-2022-0249

References

Advisorygithub.com · GHSA g5gj 9ggf 9vmq Advisorydebian.org · dsa 5041 Advisorynvd.nist.gov · CVE 2021 3908 Webgithub.com · v1.4.0 Packagegithub.com · cfrpki

Related vulnerabilities

This CVE is high severity; 4 of 8 other CVEs affecting cfrpki are rated as high or higher (top: high).

CVE-2022-3616GHSA-3jhm-87m6-x959GHSA-8459-6rc9-8vf8CVE-2021-3978CVE-2021-3910CVE-2021-3909CVE-2021-3907CVE-2021-3912

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026

CVE-2021-3908 — cfrpki

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

For more information

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-3908 in your dependencies?