CVE-2021-20806
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 · uneditedOpen redirect vulnerability in Cybozu Remote Service 3.0.0 to 3.1.9 allows remote attackers to redirect users to arbitrary web sites and conduct phishing attacks via unspecified vectors.
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 confidenceCybozu Remote Service versions 3.0.0 through 3.1.9 contain an open redirect vulnerability where the application fails to properly validate redirect targets, allowing attackers to craft malicious URLs that redirect users to arbitrary external sites for phishing purposes.
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>= 3.0.0, <= 3.1.9CVSS 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 checksWork through these to decide whether this CVE applies to you.
-
Check Cybozu Remote Service Manager versionAccess the product's admin console or system information page, or check the installer/version file in the installation directory. Common paths may include /var/lib/cybozu or C:\Program Files\Cybozu\RemoteService\Affected if The installed version is 3.0.0, 3.1.0, 3.1.1, 3.1.2, 3.1.3, 3.1.4, 3.1.5, 3.1.6, 3.1.7, 3.1.8, or 3.1.9 (any version from 3.0.0 through 3.1.9)
Your environment is affected if Cybozu Remote Service Manager version 3.0.0 through 3.1.9 is installed and the web interface is accessible.
Generated from the published advisory. Verify against your own configuration.
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.
dbcve · scopedUpgrade Cybozu Remote Service to version 3.1.10 or later. As an interim measure, implement server-side validation of all redirect parameters to ensure they point to trusted domains only.
Cybozu Remote Service 3.2.0 or later
- 1. Back up your current Cybozu Remote Service installation and database
- 2. Download the latest version of Cybozu Remote Service from the official vendor site (kb.cybozu.support)
- 3. Stop the Remote Service Manager service
- 4. Install the upgraded version (3.2.0 or later) following the vendor's installation guide
- 5. Verify the installation and ensure the service starts correctly
- 6. Test that the open redirect vulnerability is no longer present
- 7. Monitor system logs for any unusual activity
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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
Free · runs locallyCheck whether your project pulls in CVE-2021-20806 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-20806 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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