# CVE-2021-31739: Cross-site scripting in n/a

> An attacker can inject malicious scripts via recipient addresses in SEPPmail, potentially leading to session hijacking or code execution.

- **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:** 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:** 18 Nov 2022
- **Updated:** 29 Apr 2025
- **Also known as:** GHSA-5q2f-65mc-6jvf

## What is CVE-2021-31739?

CVE-2021-31739 is a medium-severity cross-site scripting vulnerability in n/a, published on 18 Nov 2022. 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

The SEPPmail solution is vulnerable to a Cross-Site Scripting vulnerability (XSS), because user input is not correctly encoded in HTML attributes when returned by the server.SEPPmail 11.1.10 allows XSS via a recipient address.

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

## Which versions are affected by CVE-2021-31739?

It affects 1 product.


Products: Seppmail Seppmail.

## How do I fix CVE-2021-31739?

No fix has been published for CVE-2021-31739 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-31739 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-31739 exists.

## Other vulnerabilities in n/a

- [CVE-2026-2743](https://insights.sbomify.com/CVE-2026-2743/): SEPPmail User Web Interface Arbitrary File Write to RCE (critical 10.0)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-31739 and fix it if it is affected.

What it is: CVE-2021-31739 is a medium-severity cross-site scripting vulnerability in n/a, published on 18 Nov 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-31739 exists.

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-2021-31739/ (Markdown: https://insights.sbomify.com/CVE-2021-31739/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-31739
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-31739
- OSV: https://osv.dev/vulnerability/CVE-2021-31739

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-31739/
Summaries are generated and may contain mistakes; the official description above is the record.