No exploitation reported

CVE-2020-3509

No exploitation reported by the sources we read.

Published2020-09-24
WeaknessCWE-203 · CWE-388

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

A vulnerability in the DHCP message handler of Cisco IOS XE Software for Cisco cBR-8 Converged Broadband Routers could allow an unauthenticated, remote attacker to cause the supervisor to crash, which could result in a denial of service (DoS) condition. The vulnerability is due to insufficient error handling when DHCP version 4 (DHCPv4) messages are parsed. An attacker could exploit this vulnerability by sending a malicious DHCPv4 message to or through a WAN interface of an affected device. A successful exploit could allow the attacker to cause a reload of the affected device. Note: On Cisco cBR-8 Converged Broadband Routers, all of the following are considered WAN interfaces: 10 Gbps Ethernet interfaces 100 Gbps Ethernet interfaces Port channel interfaces that include multiple 10 and/or 100 Gbps Ethernet interfaces

Timeline

dates in UTC

2020-09-2418:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2020-3509?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2020-3509?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Cisco ios xeversion to verify

Branch	Affected	Fixed in	Source
16.7	= 16.7\(1\)	no fix published	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

tools.cisco.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

CISA-ADPSSVC decisionnone2024-11-13
OpenCVESSVC decisionnone—
NVDCVSS 3.18.6read 2026-10-23
CNACVSS 3.08.6read 2026-10-23
NVDCVSS 2.07.8read 2026-10-23
CNAweakness (CWE)CWE-388read 2026-10-23
NVDweakness (CWE)CWE-203read 2026-10-23
FIRST EPSSEPSS score1.4 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Published: 2020-09-24
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2020-3509?

Is CVE-2020-3509 actively exploited?

Active exploitation of CVE-2020-3509 has not been confirmed. Its EPSS score was 1.4% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2020-3509?

CVE-2020-3509 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

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