VulnerabilityPublished 12 Mar 2025Updated 19 Jul 2025

CVE-2025-25566: SoftEtherVPN · Memory Leak

Source CVE Database V5

Not known to be exploited · CVSS 5.6 Medium.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

5.6Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
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 12 Mar 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

AI-suggested

1. Monitor memory usage of SoftEtherVPN instances closely, especially on Unix/Linux systems, to detect abnormal increases that may indicate exploitation of the memory leak. 2. Limit exposure of the SoftEtherVPN command-line tools to untrusted users or networks, as the vulnerability is triggered via command-line operations. 3. Implement strict network segmentation and firewall rules to restrict access to VPN management interfaces. 4. 5. Employ resource limits (e.g., cgroups or ulimit on Linux) to constrain memory usage of the VPN process, preventing system-wide impact from leaks. 6. Consider alternative VPN solutions or versions if the risk is unacceptable and no timely patch is available. 7. Conduct penetration testing and vulnerability assessments focusing on VPN infrastructure to identify potential exploitation paths. 8. Maintain incident response readiness to quickly address any denial of service or service degradation events related to VPN availability.

Description

Memory Leak vulnerability in SoftEtherVPN 5.02.5187 allows an attacker to cause a denial of service via the UnixMemoryAlloc function. NOTE: the Supplier disputes this because the behavior is limited to a single allocation of a few hundred bytes with a command-line tool.

Impact

For European organizations, the impact of CVE-2025-25566 is primarily related to availability degradation of SoftEtherVPN services. SoftEtherVPN is an open-source VPN solution used by various organizations for secure remote access. A memory leak, even if limited, can cause gradual resource exhaustion, potentially leading to service interruptions or crashes under sustained exploitation. This can disrupt secure communications, remote work capabilities, and access to internal resources, which is critical for business continuity. Confidentiality and integrity impacts are low but not negligible, as denial of service can indirectly affect security operations. The medium CVSS score reflects that exploitation is possible remotely without privileges but requires high attack complexity, reducing the likelihood of widespread automated attacks. European organizations relying on SoftEtherVPN for critical infrastructure or sensitive communications should consider the risk, especially in sectors like finance, government, and healthcare where VPN availability is essential. The lack of known exploits and limited memory leak size reduces immediate threat but does not eliminate risk from targeted attackers or combined attack vectors.

CWE-401Missing Release of Memory after Effective Lifetime (opens in a new tab)
Variant weaknessLikelihood of exploit: Medium
The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.
Implementation · Libraries or Frameworks
Choose a language or tool that provides automatic memory management, or makes manual memory management less error-prone.
Architecture and Design
Use an abstraction library to abstract away risky APIs. Not a complete solution.
Architecture and Design · Build and Compilation
Consider using the Boehm-Demers-Weiser garbage collector (bdwgc), which can help avoid leaks.
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 19 Jul 2025, 20:32 UTC

WeaknessesCWE-401

Technical details

References

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