CVE-2021-35207
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 · uneditedAn issue was discovered in Zimbra Collaboration Suite 8.8 before 8.8.15 Patch 23 and 9.0 before 9.0.0 Patch 16. An XSS vulnerability exists in the login component of Zimbra Web Client, in which an attacker can execute arbitrary JavaScript by adding executable JavaScript to the loginErrorCode parameter of the login url.
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 confidenceThis is a reflected XSS vulnerability in the Zimbra Web Client login component. Attackers can inject arbitrary JavaScript code via the loginErrorCode parameter in the login URL, which gets executed in the victim's browser when the error page is rendered without proper sanitization.
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>= 8.8, < 8.8.15= 8.8.15= 9.0.0CVSS 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.
-
Identify installed Zimbra versionRun: zmcontrol -v or check /opt/zimbra/.git describe --tags` to determine the exact Zimbra Collaboration version installedAffected if Version is 8.8.x (any patch before 15), 8.8.15 (any patch before 23), or 9.0.0 (any patch before 16)
-
Confirm web client is accessibleCheck if the Zimbra web interface port (usually 8443 or 443) is open and responding at /zimbra/h/login or /mail/Affected if The Zimbra Web Client login page is exposed and reachable over HTTP/HTTPS
-
Inspect login URL handling of loginErrorCodeSubmit a login request with a crafted loginErrorCode parameter such as ?loginErrorCode=<script>alert(1)</script> and observe if the raw script tag appears in the response page source without encodingAffected if The error page reflects the loginErrorCode parameter value unescaped in HTML (script tags execute or appear verbatim in page source)
-
Review web server access logs for loginErrorCodeCheck Apache or Nginx access logs in /opt/zimbra/log/ for requests containing loginErrorCode parameters with potential XSS payloadsAffected if Unsanitized loginErrorCode values are being logged and reflected in error responses
You are affected if your Zimbra version falls within 8.8.x before 8.8.15 Patch 23, 8.8.15 before Patch 23, or 9.0.0 before Patch 16 AND the loginErrorCode parameter is reflected unescaped in the login error page.
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.
From vendor data8.8.15
Apply the vendor patch (8.8.15 Patch 23 or 9.0.0 Patch 16) to the affected Zimbra Collaboration Suite installation to remediate the XSS vulnerability in the login component.
- Consultation2.0 h
- Implementation2.0 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 $2,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-35207 — 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-2021-35207 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
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.
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.
- 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