# CVE-2026-33370: Cross-site scripting in n/a

> Attackers can execute arbitrary scripts in victim sessions via malicious files in Zimbra Briefcase, leading to data theft or account takeover.

- **Severity:** Medium 6.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 20 Mar 2026
- **Updated:** 23 Mar 2026
- **Also known as:** GHSA-cwch-jfrm-2v7r

## What is CVE-2026-33370?

CVE-2026-33370 is a medium-severity cross-site scripting vulnerability in Synacor Zimbra Collaboration Suite, published on 20 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

An issue was discovered in Zimbra Collaboration (ZCS) 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Zimbra Briefcase feature due to insufficient sanitization of specific uploaded file types. When a user opens a publicly shared Briefcase file containing malicious scripts, the embedded JavaScript executes in the context of the user's session. This allows an attacker to run arbitrary scripts, potentially leading to data exfiltration or other unauthorized actions on behalf of the victim user.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-33370?

It affects 1 product.


Products: Synacor Zimbra Collaboration Suite.

## How do I fix CVE-2026-33370?

No fix has been published for CVE-2026-33370 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-33370 being exploited?

There is no known exploitation of CVE-2026-33370 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-2026-33370 and fix it if it is affected.

What it is: CVE-2026-33370 is a medium-severity cross-site scripting vulnerability in Synacor Zimbra Collaboration Suite, published on 20 Mar 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-33370 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-2026-33370/ (Markdown: https://insights.sbomify.com/CVE-2026-33370/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33370
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33370
- OSV: https://osv.dev/vulnerability/CVE-2026-33370

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-33370/
Summaries are generated and may contain mistakes; the official description above is the record.