# CVE-2026-93634: Zimbra Collaboration Suite Cross-Account Authorization Bypass via Forged Shared-File Records


- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 23 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** GHSA-8563-28f8-ph7v

## What is CVE-2026-93634?

CVE-2026-93634 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite, published on 23 Oct 2026. 

### Official description

A cross-account authorization vulnerability in Zimbra Collaboration Suite (ZCS) allows an authenticated user to insert forged shared-file records into another user's mailbox through FileSharedWithMeRequest. The request bypasses delegated-account authorization and accepts attacker-selected file metadata, owner identifiers and declared sizes without validating a corresponding document share. An attacker can plant entries attributed to another real local account without that account sharing a document. No victim interaction is required. ZCS 10.1.16 and 10.1.20 are affected.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-93634?

It affects 1 product.


Products: Synacor Zimbra Collaboration Suite.

## How do I fix CVE-2026-93634?

No fix has been published for CVE-2026-93634 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-93634 being exploited?

There is no known exploitation of CVE-2026-93634 in the wild and no public exploit code.

## Other vulnerabilities in Synacor Zimbra Collaboration Suite

- [CVE-2024-45519](https://insights.sbomify.com/CVE-2024-45519/): Synacor Zimbra Collaboration Suite (ZCS) Command Execution (critical 10.0, exploited in the wild)
- [CVE-2022-41352](https://insights.sbomify.com/CVE-2022-41352/): Synacor Zimbra Collaboration Suite (ZCS) Arbitrary File Upload (critical 9.8, exploited in the wild)
- [CVE-2022-37042](https://insights.sbomify.com/CVE-2022-37042/): Synacor Zimbra Collaboration Suite (ZCS) Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2022-27924](https://insights.sbomify.com/CVE-2022-27924/): Synacor Zimbra Collaboration Suite (ZCS) Command Injection (critical 9.8, exploited in the wild)
- [CVE-2020-7796](https://insights.sbomify.com/CVE-2020-7796/): Synacor Zimbra Collaboration Suite (ZCS) Server-Side Request Forgery (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93634 and fix it if it is affected.

What it is: CVE-2026-93634 is a medium-severity vulnerability in Synacor Zimbra Collaboration Suite, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-93634 in the wild and no public exploit code.

Affected product: Synacor Zimbra Collaboration Suite. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-93634/ (Markdown: https://insights.sbomify.com/CVE-2026-93634/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93634
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93634
- OSV: https://osv.dev/vulnerability/CVE-2026-93634

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93634/
Summaries are generated and may contain mistakes; the official description above is the record.