# CVE-2025-27915: Synacor Zimbra Collaboration Suite (ZCS) Cross-site Scripting

> Stored XSS in Zimbra allows attackers to execute JavaScript via malicious ICS files, enabling account takeover and data exfiltration.

- **Severity:** Medium 5.4 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Yes, since 7 Oct 2025 (CISA KEV)
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 12 Mar 2025
- **Updated:** 26 Feb 2026
- **Also known as:** GHSA-5rg8-g76j-7fw7

## What is CVE-2025-27915?

CVE-2025-27915 is a medium-severity cross-site scripting vulnerability in Synacor Zimbra Collaboration Suite, published on 12 Mar 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

An issue was discovered in Zimbra Collaboration (ZCS) 9.0 and 10.0 and 10.1. A stored cross-site scripting (XSS) vulnerability exists in the Classic Web Client due to insufficient sanitization of HTML content in ICS files. When a user views an e-mail message containing a malicious ICS entry, its embedded JavaScript executes via an ontoggle event inside a <details> tag. This allows an attacker to run arbitrary JavaScript within the victim's session, potentially leading to unauthorized actions such as setting e-mail filters to redirect messages to an attacker-controlled address. As a result, an attacker can perform unauthorized actions on the victim's account, including e-mail redirection and data exfiltration.

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

## Which versions are affected by CVE-2025-27915?

It affects 1 product.


Products: Synacor Zimbra Collaboration Suite.

## How do I fix CVE-2025-27915?

No fix has been published for CVE-2025-27915 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 28 Oct 2025.

## Is CVE-2025-27915 being exploited?

Yes. Attackers have exploited CVE-2025-27915 in the wild since at least 7 Oct 2025.

Public exploit code:

- Zimbra - Cross-Site Scripting via ICS Files (nuclei): http/cves/2025/CVE-2025-27915.yaml

## 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-2025-27915 and fix it if it is affected.

What it is: CVE-2025-27915 is a medium-severity cross-site scripting vulnerability in Synacor Zimbra Collaboration Suite, published on 12 Mar 2025. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: Yes. Attackers have exploited CVE-2025-27915 in the wild since at least 7 Oct 2025.

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-2025-27915/ (Markdown: https://insights.sbomify.com/CVE-2025-27915/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-27915
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-27915
- OSV: https://osv.dev/vulnerability/CVE-2025-27915

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-27915/
Summaries are generated and may contain mistakes; the official description above is the record.