# CVE-2026-93630: Zimbra Collaboration Suite Email HTML Sanitizer Bypass via Hostname Canonicalization


- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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-34q7-82vg-cv73

## What is CVE-2026-93630?

CVE-2026-93630 is a medium-severity vulnerability in Zimbra Collaboration Suite, published on 23 Oct 2026. 

### Official description

A hostname canonicalization vulnerability in the email HTML sanitizers of Zimbra Collaboration Suite (ZCS) allows an unauthenticated sender to bypass the restriction on forms that target the Zimbra host. DefangFilter and the OWASP ActionAttributePolicy compare the form-action hostname with the request hostname before browser URL canonicalization. A percent-encoded hostname can therefore survive sanitization while the browser submits the form to the normal Zimbra origin with the recipient's authentication cookie. This permits authenticated form requests from a crafted email after the recipient opens it in Classic and submits the form. The issue is present in ZCS 10.1.16 and 10.1.21. It does not bypass an endpoint's CSRF-token checks; a state-changing attack additionally requires an endpoint that accepts the resulting request without that protection.

Weakness: CWE-180 (Incorrect Behavior Order: Validate Before Canonicalize)

## Which versions are affected by CVE-2026-93630?


## How do I fix CVE-2026-93630?

No fix has been published for CVE-2026-93630 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-93630 being exploited?

There is no known exploitation of CVE-2026-93630 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93630 and fix it if it is affected.

What it is: CVE-2026-93630 is a medium-severity vulnerability in Zimbra Collaboration Suite, published on 23 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-93630 in the wild and no public exploit code.

Affected product: 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-2026-93630/ (Markdown: https://insights.sbomify.com/CVE-2026-93630/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93630
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93630
- OSV: https://osv.dev/vulnerability/CVE-2026-93630

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93630/
Summaries are generated and may contain mistakes; the official description above is the record.