CVE-2021-27821: The Web Interface for OpenWRT LuCI version 19.07 and lower has been discovered to have a cross-site scripting

Q: How do I fix CVE-2021-27821?

luci: upgrade to newer than 19.07.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-27821 being exploited?

CVE-2021-27821 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-27821 affect?

CVE-2021-27821 affects luci. Severity is medium (CVSS 6.1). The Web Interface for OpenWRT LuCI version 19.07 and lower has been discovered to have a cross-site scripting vulnerability.

Q: How urgent is CVE-2021-27821?

Priority 33/100. No elevated risk signals yet.

Routine

MEDIUM 6.1UPGRADE

CVE-2021-27821 is a medium-severity flaw (CVSS 6.1) affecting luci. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.6% (top 52%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-05-25
Last modified	2026-07-09

Publisher (CNA): MITRE · Vendor: openwrt

Last updated 2026-07-09 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-05-25 14:15 UTCPublished CVE record published
2026-07-09 01:16 UTCUpdated Record last modified

openwrt luci UPGRADE

Affected: <= 19.07.0

Fixed in: newer than 19.07.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy luci || rpm -q luci || luci --version

2. UPGRADE to newer than 19.07.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade luci

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade luci

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-27821?

luci: upgrade to newer than 19.07.0. Exact commands for each OS are on this page.

Is CVE-2021-27821 being exploited?

CVE-2021-27821 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-27821 affect?

CVE-2021-27821 affects luci. Severity is medium (CVSS 6.1). The Web Interface for OpenWRT LuCI version 19.07 and lower has been discovered to have a cross-site scripting vulnerability.

How urgent is CVE-2021-27821?

Priority 33/100. No elevated risk signals yet.

Software pages

OpenWrt vulnerabilities

Related CVEs

CVE-2026-32721 HIGH 8.6 UPGRADE UPGRADE LuCI is the OpenWrt Configuration Interface
CVE-2023-3085 LOW 3.5 UPGRADE A vulnerability, which was classified as problematic, has been found in X-WRT luci up to 22.10_b202303061504
CVE-2023-24181 MEDIUM 5.4 DOWNGRADE LuCI openwrt-22.03 branch git-22.361.69894-438c598 was discovered to contain a reflected cross-site scripting
CVE-2022-41435 MEDIUM 5.4 DOWNGRADE OpenWRT LuCI version git-22.140.66206-02913be was discovered to contain a stored cross-site scripting (XSS) vu
CVE-2020-10871 MEDIUM 5.3 DOWNGRADE In OpenWrt LuCI git-20.x, remote unauthenticated attackers can retrieve the list of installed packages and ser

References

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