# CVE-2025-3929 — MDaemon Email Server

> As of 2025-04-29, CVE-2025-3929 is a MEDIUM-severity vulnerability in MDaemon Email Server, CVSS v3.1 6.1, EPSS 0.6% (48.3th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2025-3929, most recently “Operation RoundPress: TA458 Deploys SpyPress Malware via Half-Click Webmail Zero-Days (CVE-2025-27915, CVE-2025-3929, CVE-2026-8496)”.

**Last updated:** 2025-04-29

## What is CVE-2025-3929?

An XSS issue was discovered in MDaemon Email Server version 25.0.1 and below. An attacker can send a specially crafted HTML e-mail message with JavaScript in an img tag. This could allow a remote attacker to load arbitrary JavaScript code in the context of a webmail user's browser window, and access user data.

The record classifies CVE-2025-3929 under weakness class [CWE-79](https://intel.threadlinqs.com/cwe/CWE-79). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 524 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 6.1 — MEDIUM (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N`)
- **CVSS v4.0 base score:** 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N`)
- **EPSS (FIRST):** 0.6% probability of exploitation in the next 30 days, higher than 48.3% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 7/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2025-04-29

## Is CVE-2025-3929 being exploited?

Weaponised exploit code for CVE-2025-3929 is publicly available. 1 public proof-of-concept repository is tracked for this identifier.

- [trickest/cve](https://github.com/trickest/cve/blob/main/2025/CVE-2025-3929.md) (trickest)

## Affected products and versions

- **MDaemon**: Email Server

## How to fix CVE-2025-3929

No vendor patch reference has been recorded for CVE-2025-3929 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2025-3929

1 tracked threat in the Threadlinqs corpus references CVE-2025-3929, either in the campaign’s CVE list or as an indicator on the campaign record.

- [Operation RoundPress: TA458 Deploys SpyPress Malware via Half-Click Webmail Zero-Days (CVE-2025-27915, CVE-2025-3929, CVE-2026-8496)](https://intel.threadlinqs.com/threat/TL-2026-2579) — CRITICAL · 2026-07-23

## Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on 2026-09-28. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [mdaemon.com](https://mdaemon.com/pages/downloads-critical-updates)

Canonical: https://intel.threadlinqs.com/cve/CVE-2025-3929
Full detection coverage and IOCs for threats exploiting CVE-2025-3929 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp