CVE-2025-2848VulnerabilityPublished 4 Dec 2025

CVE-2025-2848: Synology Mail Server · Missing Authorization

Affects Synology Mail ServerSource CVE Database V5

Not known to be exploited · CVSS 6.3 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

6.3Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 30% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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: None: The vulnerable system can be exploited without any interaction from any user.
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: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 4 Dec 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 2026-10-26.

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
Synology Synology Mail Server	Affected *	Fixed in–

AI-suggested

1. Enforce strict access controls: Limit administrative and configuration access to Synology Mail Server to only trusted personnel using role-based access control (RBAC). 2. Implement multi-factor authentication (MFA) for all accounts with access to the mail server to reduce the risk of credential compromise. 3. Monitor and audit logs regularly for unusual configuration changes or access patterns that could indicate exploitation attempts. 4. Apply the principle of least privilege by ensuring users have only the minimum permissions necessary to perform their roles. 5. Network segmentation: Isolate the mail server from general user networks to reduce exposure to unauthorized access. 6. Stay updated with Synology security advisories and apply patches promptly once available. 7. Consider deploying intrusion detection/prevention systems (IDS/IPS) to detect anomalous activities targeting the mail server. 8. Conduct regular security awareness training to reduce the risk of credential theft via phishing or social engineering. 9. Review and harden mail server configurations to disable unnecessary features and services that could be exploited. 10. Prepare incident response plans specifically addressing mail server compromise scenarios.

Description

A vulnerability in Synology Mail Server allows remote authenticated attackers to read and write non-sensitive settings, and disable some non-critical functions.

Impact

For European organizations, the impact of CVE-2025-2848 primarily involves potential disruption or misconfiguration of mail server operations rather than direct data breaches or critical system compromise. Attackers with valid credentials could alter non-sensitive settings or disable non-critical functions, which might degrade service availability or cause operational inefficiencies. This could affect business communications, especially in sectors where email is critical for daily operations such as finance, healthcare, and government. While the vulnerability does not expose sensitive data directly, unauthorized configuration changes could be leveraged as part of a broader attack chain or to create persistent operational issues. The requirement for authenticated access limits the attack surface to insiders or attackers who have already compromised user credentials, emphasizing the need for strong access control and credential management. European organizations with Synology Mail Server deployments should consider the risk of insider threats or credential theft as part of their threat model. The absence of known exploits reduces immediate risk but does not eliminate the need for proactive mitigation.

References

synology.com/en-global/security/advisory/Synology_SA_25_05 (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Dec 2025, 15:32 UTC

Technical details

References

Community reviews

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