CriticalCVE-2024-11182

    Stored XSS vulnerability in MDaemon Email Server (CVE-2024-11182)

    Published In CISA KEV since Sources: pwn.watch, CVE.org

    Share

    What is affected, what to do

    An XSS issue was discovered in MDaemon Email Server before version 24.5.1c. An attacker can send an HTML e-mail message with JavaScript in an img tag.

    The vulnerability is being actively exploited; treat it as a priority. Update mdaemon to version 24.5.1. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • MDaemon Email Server lte *..24.5.0

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    6.1

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: pwn.watch, CVE.org

    33.3 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 98.4

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    214.71 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploited
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    6.1
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    5.3
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    33.3 %
    Elevated — model estimates 10-50% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    98.4
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CISA assessment (SSVC)
    Exploitation: active · not automatable · Technical impact: total
    Source: CISA Vulnrichment, as of 21 May 2025
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-79

    Response and mitigation

    Why act now?

    Prioritisation rationale

    The flaw is network-reachable without authentication. The only requirement is delivering a crafted email that the victim opens in webmail. The formal severity reads as moderate, but the scenario is tailor-made for targeted espionage: it is typically used to steal credentials, harvest mailbox content and contacts, and plant persistent forwarding rules. CISA does not flag ransomware use. Exploitation likelihood is very high, placing it among the CVEs most likely to be exploited. Organisations exposing MDaemon Webmail to the internet should treat the patch as top priority, especially government, defence and critical-infrastructure suppliers. Sites that don't use or expose webmail can fold it into the regular cycle, with elevated urgency.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Patch now: Upgrade every MDaemon Email Server instance to 24.5.1c or later. All versions before 24.5.1c, including 24.5.0, are vulnerable. Confirm the running build in MDaemon Remote Administration or the About dialog. Back up the configuration and mail stores before upgrading. Further fix details are in the vendor advisory.
      • Cut webmail exposure: Until patched, block internet access to MDaemon Webmail (formerly WorldClient; default 3000/TCP, or 443/TCP behind a reverse proxy). Allow access only via VPN or ZTNA, and move users temporarily to IMAP or desktop clients.
      • Retro-hunt mailboxes: Search gateway logs and the mail archive for inbound HTML messages whose <img> tags carry event handlers (onerror=, onload=) or javascript: URIs. Quarantine any hits and identify the recipients.
      • Remediate affected accounts: For recipients who opened such a message in webmail, reset the password and kill active webmail sessions. Then audit forwarding and filter rules, app passwords and 2FA settings for unauthorised changes.
      • Assess reporting duties: If mailbox data exfiltration is confirmed, evaluate NIS2 notification timelines (early warning within 24 h) and involve your DPO.

    2. Runbook step 2

      Mitigation layers

      • Network segmentation: Restrict the webmail front end to trusted networks or VPN. Limit egress from the MDaemon server to what operations require (SMTP, updates).
      • Mail gateway / content filtering: Sanitise inbound HTML. Strip event-handler attributes (on[a-z]+=) from <img>, <svg> and <iframe>, and neutralise javascript: and data:text/html URIs. Alternatively, force text/plain rendering for external senders.
      • Reverse proxy / WAF: Inject a strict Content-Security-Policy in front of webmail (script-src 'self', no unsafe-inline, connect-src 'self'). This stops injected code from beaconing to attacker hosts. Test compatibility with the webmail UI before rollout.
      • IAM / least privilege: Enforce MFA on all webmail accounts. Administrators should not read external mail in the same webmail session they use to administer the server. Block automatic external forwarding server-side.
      • Endpoint and browser hardening: Serve webmail through remote browser isolation where possible. Use browser policy to disable password saving for the webmail domain, because payloads can scrape autofilled credential fields.

    3. Runbook step 3

      Detection rules

      • Mail gateway / MTA logs: Flag inbound bodies matching <img[^>]+(onerror|onload)\s*= or src\s*=\s*["']?javascript:. As a Sigma shape, use logsource mail with body|re: '<img[^>]+on(error|load)=' at level high.
      • Proxy / Zeek HTTP logs: Look for browser requests to rare external domains whose Referer is the webmail host. KQL example: CommonSecurityLog | where RequestContext has "webmail.example.com" and DestinationHostName !endswith "example.com".
      • Webmail access logs: Bursts of API or form requests within seconds of a message being opened point to scripted actions. Typical examples are bulk message or contact retrieval and changes to filter/forwarding rules, app passwords or 2FA.
      • MDaemon configuration audit: Alert on new external forwarding rules and newly created app passwords. Correlate them with first-seen login IPs shortly after suspicious mail delivery.
      • Outbound SMTP: A sudden spike in forwarded volume from a single mailbox to freemail or newly registered domains is a strong signal (SPL: index=mail action=forward | stats count by user, recipient_domain).

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    An XSS issue was discovered in MDaemon Email Server before version 24.5.1c. An attacker can send an 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.

    Source: pwn.watch, NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    MDaemonEmail Server
    • ≤ 24.5.0
    • —
    mdaemonmdaemon
    • < 24.5.1
    • 24.5.1

    Vendors and products

    Weakness classes (CWE)

    • CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

      Base

      The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

      Entry at MITRE CWE-79

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited

    References & sources

    • files.mdaemon.comMDaemon advisory: MDaemon Email ServerRelease notes, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2024-11182government-resource, US government resource
    • pwn.watchpwn.watch: MDaemon Email Server: Email Server Cross-Site Scripting (XSS) Vulnerabilitypwn-watch
    • mdaemon.comMDaemon advisory: MDaemon Email Serverpwn-watch
    • NVD (NIST)NVD: CVE-2024-11182pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
    Embed badge

    Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

    Badge preview for CVE-2024-11182
    <a href="https://intel.neosec.eu/en/cve/CVE-2024-11182"><img src="https://intel.neosec.eu/badge/cve/CVE-2024-11182.svg?lang=en" alt="CVE-2024-11182 – NEOSEC Intel" height="20"></a>