LiveActive security incident?Get immediate response
CVE Record

CVE-2021-35208: An issue was discovered in ZmMailMsgView.js in the Calendar Invite component in Zimbra Collaboration Suite...

An issue was discovered in ZmMailMsgView.js in the Calendar Invite component in Zimbra Collaboration Suite 8.8.x before 8.8.15 Patch 23. An attacker could place HTML containing executable JavaScript inside element attributes. This markup becomes unescaped, causing arbitrary markup to be injected into the document.

UnknownCVSS not scoredNot KEV-listedUpdated
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

A vulnerable Zimbra calendar invite view could turn crafted HTML into JavaScript in a user's browser. For organizations running affected Zimbra webmail, a malicious email or invite could threaten mailbox confidentiality and user sessions when viewed.

Executive priority

Treat this as a high-priority patch and exposure review for any Zimbra environment. The issue targets webmail users through content handling, so user interaction can translate into mailbox or session risk.

Technical view

CVE-2021-35208 affects ZmMailMsgView.js in the Zimbra Calendar Invite component. HTML with executable JavaScript inside element attributes can become unescaped, causing arbitrary markup injection. The provided CVE text identifies Zimbra Collaboration Suite 8.8.x before 8.8.15 Patch 23.

Likely exposure

Exposure is most likely where Zimbra Collaboration Suite 8.8.x is still below 8.8.15 Patch 23 and users can receive untrusted calendar invites or email content.

Exploitation context

The bundle does not show CISA KEV listing or active exploitation evidence. SonarSource published public technical analysis about Zimbra webmail compromise via email, which raises defender urgency without proving current exploitation.

Researcher notes

Evidence supports an HTML/JavaScript escaping failure in the calendar invite rendering path, not a server-side remote code execution claim. Patch boundary is clear for 8.8.x; broader affected-version claims are not established in the bundle.

Mitigation direction

  • Upgrade affected Zimbra 8.8.x deployments to 8.8.15 Patch 23 or later guidance.
  • Review Zimbra 9.0.0 Patch 16 notes if running Zimbra 9.0.0.
  • Check Zimbra security advisories for any later superseding patches.
  • Restrict exposure of Zimbra webmail where business operations allow.
  • Warn users about suspicious calendar invites until patch status is confirmed.

Validation and detection

  • Inventory all Zimbra Collaboration Suite versions and patch levels.
  • Confirm no 8.8.x systems are below 8.8.15 Patch 23.
  • Review Zimbra logs for suspicious webmail access after calendar invite views.
  • Check email security telemetry for suspicious calendar invite campaigns.
  • Verify remediation against Zimbra advisory and release-note references.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cve · low confidence lookup

CVE-2021-35208 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

Open ATT&CK lookup
Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
6Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/an/an/aListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.