Is CVE-2021-3761 in the CISA KEV catalog?

No. CVE-2021-3761 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2021-3761?

CVE-2021-3761 has a CVSS v3 base score of 7.5 (HIGH).

What is the EPSS score for CVE-2021-3761?

CVE-2021-3761 has an EPSS score of 1.22% (65th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2021-3761?

Upgrade cfrpki on debian 11 to 1.4.2-1~deb11u1 or later.

CVE & CISA-KEV Catalog

CVE-2021-3761

HIGH

7.5

CVSS v3

NVD

Description

Any CA issuer in the RPKI can trick OctoRPKI prior to 1.3.0 into emitting an invalid VRP "MaxLength" value, causing RTR sessions to terminate. An attacker can use this to disable RPKI Origin Validation in a victim network (for example AS 13335 - Cloudflare) prior to launching a BGP hijack which during normal operations would be rejected as "RPKI invalid". Additionally, in certain deployments RTR session flapping in and of itself also could cause BGP routing churn, causing availability issues.

CWE-787Out-of-bounds Write

How to fix

Remediation Available

cfrpkiDebian

Fixed in:1.4.2-1~deb11u1CVE-2021-3761

Fixed in:1.3.0-1CVE-2021-3761

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityNone

IntegrityNone

AvailabilityHigh

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

Exploit Intelligence

1.22%probability of exploitation in 30 days

65thpercentile

Moderate risk: more likely to be exploited than 65% of all known CVEs.

References

Patch1

github.com

Third-Party Advisory1

debian.org

Related Vulnerabilities

Other CWE-787 (Out-of-bounds Write) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-22457	Critical	9.0	100%	KEV + Ransom	Fix
CVE-2025-0282	Critical	9.0	100%	KEV + Ransom	-
CVE-2015-3113	Critical	9.8	100%	KEV	Fix
CVE-2021-20038	Critical	9.8	100%	KEV + Ransom	-
CVE-2023-4863	High	8.8	100%	KEV	Fix
CVE-2020-16040	Medium	6.5	100%	-	Fix

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.