dbcve.org
LuciApplication · Openwrt

CVE-2021-27821

MEDIUM · 6.1 CVSS v3.1 Published 2021-05-25
Fix available
A fix is available. Upgrade to after 19.07.0 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

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

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

A cross-site scripting (XSS) vulnerability exists in the LuCI web interface for OpenWRT routers affecting versions 19.07 and lower. The vulnerability allows attackers to inject malicious scripts through the web interface.

MitigationUpdate LuCI to a version newer than 19.07. In the interim, disable the LuCI web interface or restrict administrative access to trusted networks only.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
LuciApplication
Affected:<= 19.07.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify LuCI web interface is installed
    SSH to the router and run: which luci or dpkg -l | grep luci or opkg list-installed | grep luci
    Affected if LuCI package is not installed on the system, the vulnerability does not apply
  2. Check the installed LuCI version
    SSH to the router and run: luci -v or opkg list-installed | grep luci to see the version number
    Affected if The displayed version is 19.07.0 or any version lower than 19.07 (for example, 18.06, 19.07-rc1)
  3. Confirm the LuCI web interface is enabled
    Check /etc/config/luci or run: ps | grep luci to verify the web server process is running
    Affected if The LuCI service is actively running and the web interface is accessible on HTTP/HTTPS ports

The system is affected only if LuCI web interface is installed AND running with version 19.07.0 or lower.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to a release after 19.07.0
Interim mitigation

Update LuCI to a version newer than 19.07. In the interim, disable the LuCI web interface or restrict administrative access to trusted networks only.

Fix this in Luci Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,800.

Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-27821 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data