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CVE Record

CVE-2021-34807: An open redirect vulnerability exists in the /preauth Servlet in Zimbra Collaboration Suite through 9.0.

An open redirect vulnerability exists in the /preauth Servlet in Zimbra Collaboration Suite through 9.0. To exploit the vulnerability, an attacker would need to have obtained a valid zimbra auth token or a valid preauth token. Once the token is obtained, an attacker could redirect a user to any URL via isredirect=1&redirectURL= in conjunction with the token data (e.g., a valid authtoken= value).

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

This CVE is an open redirect in Zimbra Collaboration Suite. If an attacker already has a valid Zimbra auth or preauth token, they can make Zimbra send a user to an attacker-chosen website. The main concern is phishing and trust abuse, not direct server takeover from the provided evidence.

Executive priority

Prioritize assessment during the next vulnerability-management cycle. Raise urgency if Zimbra is internet-facing, preauth is enabled, or recent token compromise is suspected. No source in the bundle supports emergency active-exploitation handling.

Technical view

The /preauth Servlet in Zimbra Collaboration Suite through 9.0 permits arbitrary external redirects when supplied with valid token data and redirect controls. The source bundle does not provide CVSS, CWE, or precise fixed-version statements, but references Zimbra security and release pages for follow-up.

Likely exposure

Organizations running Zimbra Collaboration Suite through 9.0 may be exposed, especially internet-facing mail portals. Exploitation requires a valid auth or preauth token, so exposure depends on token compromise, token issuance paths, and user interaction with crafted links.

Exploitation context

The CVE source describes a token-gated open redirect. It does not cite public active exploitation, and KEV is false in the bundle. Treat this as a phishing and session-trust risk that can amplify other token theft or social-engineering incidents.

Researcher notes

Evidence is limited: no CVSS, CWE, CPE, or explicit fixed version is provided in the CVE bundle. The useful facts are the affected product/version phrase, /preauth location, valid-token prerequisite, and arbitrary redirect outcome. Validate remediation only against Zimbra guidance.

Mitigation direction

  • Review Zimbra security advisories for the vendor-confirmed fix or workaround.
  • Inventory Zimbra Collaboration Suite versions, especially deployments through 9.0.
  • Apply vendor-supported Zimbra updates after normal change validation.
  • Restrict and monitor preauth token generation and administrative access.
  • Review mail security controls for external redirect and phishing protections.

Validation and detection

  • Confirm whether any Zimbra Collaboration Suite deployment is version 9.0 or earlier.
  • Check vendor advisory and release notes against the installed patch level.
  • Review logs for suspicious /preauth redirect activity involving valid tokens.
  • Assess whether preauth token generation is limited to trusted systems.
  • Verify user-facing Zimbra URLs are covered by phishing detection controls.
Prepared
Confidence
medium
Sources
6

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

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ATT&CK lookup starting points

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description · low confidence lookup

Credential and access behavior lookup

The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2021-34807 mapping review

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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
5Source 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.