VulnerabilityPublished 21 Jul 2025Updated 22 Jul 2025

CVE-2025-52374: hmailserver · Use of Hard-coded Cryptographic Key

Affects hmailserverSource CVE Database V5

Not known to be exploited · CVSS 4.6 Medium.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

4.6Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 13% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: Required
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubhmailserver/hmailserver`pkg:github/hmailserver/hmailserver`Other threats	Affected =5.8.6 =5.6.9-beta	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately audit their hMailServer deployments to identify affected versions (5.8.6 and 5.6.9-beta). Employ strict file system permissions and monitor access logs for unusual activity. Consider isolating mail server admin consoles on segmented networks with strong authentication mechanisms. Where possible, replace the hardcoded encryption mechanism by customizing or recompiling the software with unique cryptographic keys, or migrate to alternative mail server solutions with secure credential storage. Additionally, enforce multi-factor authentication (MFA) for all admin console access to reduce the risk of credential misuse. Regularly monitor for suspicious activity and prepare incident response plans in case of compromise. Finally, stay alert for official patches or updates from hMailServer developers and apply them promptly once available.

Description

Use of hardcoded cryptographic key in Encryption.cs in hMailServer 5.8.6 and 5.6.9-beta allows attacker to decrypt passwords to other servers from hMailAdmin.exe.config file to access other hMailServer admin consoles with configured connections.

Impact

For European organizations, this vulnerability poses a significant risk to the security of email infrastructure managed by hMailServer, which is a popular open-source mail server solution used by small to medium enterprises and some public sector entities. Successful exploitation could lead to unauthorized access to multiple mail server admin consoles, allowing attackers to intercept, manipulate, or disrupt email communications. This can result in data breaches involving sensitive personal data protected under GDPR, leading to regulatory fines and reputational damage. Additionally, compromised mail servers can be used as pivot points for further network intrusion or as platforms for phishing campaigns targeting European customers or partners. The medium severity score suggests that while exploitation requires some privileges and user interaction, the potential for lateral movement and data exposure is non-trivial. Organizations relying on hMailServer for critical communications or those with interconnected mail server environments are particularly at risk. The lack of a patch at the time of disclosure increases the urgency for mitigation.

CWE-321Use of Hard-coded Cryptographic Key (opens in a new tab)
Variant weaknessLikelihood of exploit: HighOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a hard-coded, unchangeable cryptographic key.
Architecture and Design
Prevention schemes mirror that of hard-coded password storage.
OWASP Cheat Sheets
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
Cryptographic Storage (opens in a new tab)
HSTS (opens in a new tab)
OWASP ASVS 4.0.3
V2.3.1 (opens in a new tab)
V2.6.2 (opens in a new tab)
V2.8.5 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 29 Jul 2025, 01:24 UTC

WeaknessesCWE-321

Technical details

References

Community reviews

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