CVE-2021-27821 Cross-site scripting in n/a

Medium 6.1 Published 25 May 2021 Updated 9 Jul 2026

An attacker can inject malicious scripts into the OpenWRT LuCI web interface, potentially compromising user sessions or data.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2021-27821?

CVE-2021-27821 is a medium-severity cross-site scripting vulnerability in n/a, published on 25 May 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

Official description

The Web Interface for OpenWRT LuCI version 19.07 and lower has been discovered to have a cross-site scripting vulnerability.

Weakness: CWE-79

Which versions are affected by CVE-2021-27821?

It affects 1 product.

Products include Openwrt Luci.

How do I fix CVE-2021-27821?

No fix has been published for CVE-2021-27821 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2021-27821 being exploited?

There is no known exploitation of CVE-2021-27821 in the wild and no public exploit code.

Sources

Also known as GHSA-4r8j-5v22-gg78.