What is CVE-2021-20858?

CVE-2021-20858 is a medium-severity vulnerability in Elecom Wrc-2533ghbk-I, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-12-01.

How severe is CVE-2021-20858?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Elecom Wrc-2533ghbk-I

CVE-2021-20858

Cross-site scripting vulnerability in ELECOM LAN router WRC-2533GHBK-I firmware v1.20 and prior allows a remote authenticated attacker to inject an arbitrary script via unspecified vectors.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-12-01 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.006 (46.9th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 46.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: +0.000

Affected products

Elecom Wrc-2533ghbk-I
Elecom Wrc-2533ghbk-I Firmware
Elecom Co.,ltd. Lan Router — versions WRC-2533GHBK-I firmware v1.20 and prior

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

www.elecom.co.jp/news/security/20211130-01/ (Vendor Advisory)
jvn.jp/en/jp/JVN88993473/index.html (Third Party Advisory)

Frequently asked questions

What is CVE-2021-20858?: CVE-2021-20858 is a medium-severity vulnerability in Elecom Wrc-2533ghbk-I, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-12-01.
How severe is CVE-2021-20858?: Medium severity. CVSS v3 base score is 5.4 out of 10.