# CVE-2026-2743: SEPPmail User Web Interface Arbitrary File Write to RCE

> Attackers can achieve remote code execution via arbitrary file write in the large file transfer feature of the SeppMail user web interface.

- **Severity:** Critical 10.0 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:A/AU:Y`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Mar 2026
- **Updated:** 19 May 2026
- **Also known as:** GHSA-3hq3-ff7h-6mf5

## What is CVE-2026-2743?

CVE-2026-2743 is a critical vulnerability in SeppMail, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Arbitrary File Write via Path Traversal upload to Remote Code Execution in SeppMail User Web Interface. The affected feature is the large file transfer (LFT). 

This issue affects SeppMail: 15.0.2.1 and before

Weakness: CWE-434 (Unrestricted Upload of File with Dangerous Type), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-2743?

It affects 1 product.


Products: Seppmail Seppmail.

## How do I fix CVE-2026-2743?

No fix has been published for CVE-2026-2743 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-2743 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2743 exists.

## Other vulnerabilities in SeppMail

- [CVE-2026-27441](https://insights.sbomify.com/CVE-2026-27441/): PDF Password CMDi (critical 9.5)
- [CVE-2026-27442](https://insights.sbomify.com/CVE-2026-27442/): zip_attachments Path Traversal (critical 9.3)
- [CVE-2026-27443](https://insights.sbomify.com/CVE-2026-27443/): S/MIME Decryption Tag Sanitization Bypass (high 8.2)
- [CVE-2026-27444](https://insights.sbomify.com/CVE-2026-27444/): Header Email Address Parsing (high 7.8)
- [CVE-2026-2748](https://insights.sbomify.com/CVE-2026-2748/): S/MIME Certificate Subject Whitespace (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2743 and fix it if it is affected.

What it is: CVE-2026-2743 is a critical vulnerability in SeppMail, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-2743 exists.

Affected product: SeppMail. 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-2026-2743/ (Markdown: https://insights.sbomify.com/CVE-2026-2743/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2743
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2743
- OSV: https://osv.dev/vulnerability/CVE-2026-2743

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2743/
Summaries are generated and may contain mistakes; the official description above is the record.