# CVE-2026-84465: Zammad: S/MIME signature verification allows forged sender impersonation

> Attackers can forge S/MIME signatures to impersonate trusted senders in Zammad by bypassing certificate trust verification.

- **Severity:** High 7.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA: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:** 25 Sep 2026
- **Updated:** 29 Sep 2026
- **Also known as:** GHSA-m9ff-hjr3-93h4

## What is CVE-2026-84465?

CVE-2026-84465 is a high-severity vulnerability in zammad, published on 25 Sep 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

Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, when Zammad checks the digital signature on an incoming S/MIME-signed email, it does not verify that the signing certificate is genuinely trusted, it only checks whether a certificate with a matching name is already stored in the system. An attacker can create their own certificate using the name of a real, previously trusted sender and use it to send a forged email. Zammad will display that email with the same "validly signed" indicator as a genuine message from the real sender, even though the attacker never had access to that sender's actual certificate or private key. This issue is fixed in version 7.1.2.

Weakness: CWE-347 (Improper Verification of Cryptographic Signature), CWE-295 (Improper Certificate Validation), CWE-290 (Authentication Bypass by Spoofing)

## Which versions are affected by CVE-2026-84465?


## How do I fix CVE-2026-84465?

No fix has been published for CVE-2026-84465 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-84465 being exploited?

There is no known exploitation of CVE-2026-84465 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-84465 and fix it if it is affected.

What it is: CVE-2026-84465 is a high-severity vulnerability in zammad, published on 25 Sep 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-2026-84465 in the wild and no public exploit code.

Affected product: zammad. 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-2026-84465/ (Markdown: https://insights.sbomify.com/CVE-2026-84465/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84465
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84465
- OSV: https://osv.dev/vulnerability/CVE-2026-84465

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84465/
Summaries are generated and may contain mistakes; the official description above is the record.