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Improper Input ValidationWeakness · CWE-20

CVE-2025-61084

HIGH · 7.1 CVSS v3.1 Published 2025-11-05
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
77/100
Remediation priority · High
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
MDaemon Mail Server 23.5.2 validates SPF, DKIM, and DMARC using the email enclosed in angle brackets (<>) in the From: header of SMTP DATA. An attacker can craft a From: header with multiple invisible Unicode thin spaces to display a spoofed sender while passing validation, allowing email spoofing even when anti-spoofing protections are in place. NOTE: this is disputed by the Supplier because UI spoofing occurs in a client, not in a server such as MDaemon's product or any other server implementation. Also, if a client without its own spoofing protection must be used, the Header Screening feature in MDaemon's product can be employed to mitigate the client-side vulnerability.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

MDaemon validates SPF/DKIM/DMARC using the email address enclosed in angle brackets in the From: header. Attackers can insert multiple invisible Unicode thin spaces (U+200A) between characters in the displayed email address, causing it to appear as a different sender while the actual address being validated remains unchanged. This allows visual spoofing that bypasses server-side email authentication mechanisms.

MitigationEnable and configure MDaemon's Header Screening feature to detect and strip invisible Unicode characters (particularly thin spaces U+200A) from the From header email address, or implement content filtering at the mail gateway to normalize Unicode characters before delivery to end clients.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify MDaemon version
    Locate the installed MDaemon version via the MDaemon GUI (Help > About MDaemon) or by inspecting the version information in the MDaemon program directory, typically found in the executable or installation logs
    Affected if Any MDaemon version since no specific version ranges are provided and the vulnerability affects the core SPF/DKIM/DMARC validation logic for addresses with Unicode characters
  2. Verify Header Screening configuration
    Open MDaemon's Security menu > Header Screening to inspect whether rules are configured to detect and strip invisible Unicode characters, specifically thin spaces (U+200A), from the From header email address
    Affected if Header Screening is disabled or no rule specifically targets U+200A characters in the From header address
  3. Inspect recent email headers for Unicode manipulation
    Review the raw headers of recent messages in MDaemon's queue or user mailboxes, looking for the From: header address containing U+200A (thin space) characters between characters of the email address
    Affected if Messages exist with U+200A characters inserted within the displayed email address in the From header while the validating address (in angle brackets) differs from what's visually displayed
  4. Check gateway content filtering for Unicode normalization
    Examine any upstream mail gateway or content filter configurations to determine if Unicode normalization or sanitization is applied to email headers before MDaemon processing
    Affected if No Unicode normalization is configured at the mail gateway and MDaemon's Header Screening does not strip U+200A characters

The environment is affected if MDaemon is installed without Header Screening rules specifically configured to strip U+200A thin space characters from the From header email address, allowing visually spoofed messages to bypass SPF/DKIM/DMARC validation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Enable and configure MDaemon's Header Screening feature to detect and strip invisible Unicode characters (particularly thin spaces U+200A) from the From header email address, or implement content filtering at the mail gateway to normalize Unicode characters before delivery to end clients.

Recommended fix Low confidence
  1. Enable and configure the Header Screening feature in MDaemon's administrative interface
  2. Create a Header Screening rule to filter or modify From: headers containing invisible Unicode thin space characters (U+2009, U+200A, U+200B, or similar zero-width spaces)
  3. Test the Header Screening rule with crafted test emails containing thin spaces to verify detection and proper handling
  4. Monitor mail logs after implementation to confirm the rule is functioning as expected

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-61084 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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