# CVE-2024-27443: Synacor Zimbra Collaboration Suite (ZCS) Cross-Site Scripting (XSS)

> Attackers can execute arbitrary JavaScript in victim sessions via crafted calendar headers in Zimbra webmail, potentially leading to 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:** Yes, since 19 May 2025 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 12 Aug 2024
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-qrvg-mg33-q843

## What is CVE-2024-27443?

CVE-2024-27443 is a medium-severity cross-site scripting vulnerability in n/a, published on 12 Aug 2024. 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) 9.0 and 10.0. A Cross-Site Scripting (XSS) vulnerability exists in the CalendarInvite feature of the Zimbra webmail classic user interface, because of improper input validation in the handling of the calendar header. An attacker can exploit this via an email message containing a crafted calendar header with an embedded XSS payload. When a victim views this message in the Zimbra webmail classic interface, the payload is executed in the context of the victim's session, potentially leading to execution of arbitrary JavaScript code.

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

## Which versions are affected by CVE-2024-27443?

It affects 1 product.


Products: Zimbra Collaboration.

## How do I fix CVE-2024-27443?

No fix has been published for CVE-2024-27443 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 9 Jun 2025.

## Is CVE-2024-27443 being exploited?

Yes. Attackers have exploited CVE-2024-27443 in the wild since at least 19 May 2025.

Public exploit code:

- Zimbra Collaboration - Cross-Site Scripting (XSS) (nuclei): http/cves/2024/CVE-2024-27443.yaml

## Other vulnerabilities in n/a

- [CVE-2023-29381](https://insights.sbomify.com/CVE-2023-29381/): Privilege escalation in n/a (critical 9.8)
- [CVE-2023-29382](https://insights.sbomify.com/CVE-2023-29382/): Code injection in n/a (critical 9.8)
- [CVE-2022-32294](https://insights.sbomify.com/CVE-2022-32294/): Information disclosure in n/a (critical 9.8)
- [CVE-2021-35209](https://insights.sbomify.com/CVE-2021-35209/): Server-side request forgery in n/a (critical 9.8)
- [CVE-2023-50808](https://insights.sbomify.com/CVE-2023-50808/): Cross-site scripting in n/a (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-27443 and fix it if it is affected.

What it is: CVE-2024-27443 is a medium-severity cross-site scripting vulnerability in n/a, published on 12 Aug 2024. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: Yes. Attackers have exploited CVE-2024-27443 in the wild since at least 19 May 2025.

Affected product: n/a. 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-2024-27443/ (Markdown: https://insights.sbomify.com/CVE-2024-27443/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-27443
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-27443
- OSV: https://osv.dev/vulnerability/CVE-2024-27443

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From sbomify Insights: https://insights.sbomify.com/CVE-2024-27443/
Summaries are generated and may contain mistakes; the official description above is the record.