Cross-site Scripting Vulnerability in Phoenix Contact FL SWITCH SMCS series products

published 2021-06-25 5y ago modified 2026-06-17 4mo ago also EUVD-2021-8413

cvss: 7.4; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.6%; EPSS 0.6% chance of exploitation in 30 days, percentile 48%
public exploits: 0; none known

In Phoenix Contact FL SWITCH SMCS series products in multiple versions an attacker may insert malicious code via LLDP frames into the web-based management which could then be executed by the client.

Is CVE-2021-21004 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Exploit prediction

0.58% chance of exploitation in the next 30 days, higher than 48% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.4	CVSS:3.1/AV:A/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N
NVD	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD	2.0	4.3	AV:N/AC:M/Au:N/C:N/I:P/A:N

Affected products

Phoenix Contact FL SWITCH
Phoenix Contact FL NAT

Classification

Weakness

CWE-79 Improper Neutralization of Input During Web Page Generation

References

cert.vde.com /en-us/advisories/vde-2021-023
not-applicable, third-party-advisory

Sources

CVE List CVE-2021-21004
NVD CVE-2021-21004

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.