dbcve.org
Umbraco CmsApplication · Umbraco

CVE-2021-34254

MEDIUM · 6.1 CVSS v3.1 Published 2021-06-28
Fix available
A fix is available. Upgrade to 7.15.7 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
Umbraco CMS before 7.15.7 is vulnerable to Open Redirection due to insufficient url sanitization on booting.aspx.

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 · high confidence

Umbraco CMS versions before 7.15.7 contain an open redirection vulnerability in the booting.aspx page. The vulnerability stems from insufficient URL sanitization, allowing remote attackers to craft malicious URLs that redirect users to arbitrary external sites.

MitigationUpgrade Umbraco CMS to version 7.15.7 or later to obtain the fix for this open redirection vulnerability.

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
Umbraco CmsApplication
Affected:< 7.15.7

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. Identify installed Umbraco CMS version
    Inspect the web.config file in the site root for the umbracoConfiguration>settings>content>resolvedVersion setting, or check the assembly version of Umbraco.Core.dll in the /bin folder
    Affected if The detected version number is less than 7.15.7
  2. Confirm booting.aspx exists and is accessible
    Attempt to access the booting.aspx page at the site root via HTTP request (e.g., curl or browser to https://yourdomain.com/booting.aspx)
    Affected if The page loads and returns an HTTP 200 status without requiring authentication
  3. Review for suspicious redirect parameters
    Check HTTP access logs or application logs for requests to booting.aspx containing redirect-related query parameters such as returnUrl, redirect, or url
    Affected if Logs show unauthenticated requests with external or unexpected redirect destinations

Your environment is affected if the installed Umbraco CMS version is earlier than 7.15.7 and the booting.aspx page is accessible without authentication, enabling open redirect exploitation.

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 7.15.7 or later
Fixed in 7.15.7
Interim mitigation

Upgrade Umbraco CMS to version 7.15.7 or later to obtain the fix for this open redirection vulnerability.

Fix this in Umbraco Cms Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2021-34254 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

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-2021-34254 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

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