VulnerabilityPublished 7 Dec 2023Updated 18 Dec 2025

CVE-2023-41913: strongswan · Classic Buffer Overflow

Affects strongswanSource CVE Database V5

Not known to be exploited · CVSS 9.8 Critical : upgrade to 5.9.12 as a priority.

Data as of 26 Oct 2026, 13:47 UTC

CVSS 3.1 base score

9.8Critical

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

EPSS: 2.3% chance of exploitation in 30 days – higher than 83% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.9.12

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

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

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: 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: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Dec 2023
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 or the CVSS exploit maturity 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

Upgrade strongswan/strongswan to 5.9.12.

Affected software

Product	Affected	Fixed in
GitHubstrongswan/strongswan`pkg:github/strongswan/strongswan`Other threats	Affected >=5.3.0 <5.9.12	Fixed in 5.9.12

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

AI-suggested

Immediately upgrade all strongSwan installations to version 5.9.12 or later, where the vulnerability is patched.
If immediate patching is not feasible, implement network-level controls to restrict and monitor IKE_SA_INIT messages, such as firewall rules limiting VPN initiation to trusted IP addresses.
Deploy intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting anomalous or malformed IKE_SA_INIT packets indicative of exploitation attempts.
Conduct regular VPN traffic analysis to identify unusual patterns or spikes that may signal scanning or attack activity.
Enforce strict access controls and network segmentation to limit the potential lateral movement if a VPN gateway is compromised.
Maintain up-to-date asset inventories to quickly identify and remediate vulnerable strongSwan instances.
Educate security teams about this vulnerability and incorporate it into incident response plans to ensure rapid detection and containment.
Collaborate with VPN vendors and security communities to stay informed about emerging exploit techniques and mitigation strategies.

Description

strongSwan before 5.9.12 has a buffer overflow and possible unauthenticated remote code execution via a DH public value that exceeds the internal buffer in charon-tkm's DH proxy. The earliest affected version is 5.3.0. An attack can occur via a crafted IKE_SA_INIT message.

Impact

For European organizations, the impact of CVE-2023-41913 is substantial due to the widespread use of strongSwan in securing VPN communications across government, financial, healthcare, and critical infrastructure sectors. Successful exploitation can lead to unauthorized access to internal networks, data breaches, and disruption of secure communications. This could compromise sensitive personal data protected under GDPR, leading to regulatory penalties and reputational damage. The ability to execute remote code without authentication means attackers can deploy malware, establish persistent backdoors, or pivot within networks to escalate attacks. Disruption of VPN services could also impact business continuity and remote workforce operations, which remain critical in the post-pandemic hybrid work environment. The vulnerability's network-level exploitability increases the risk of automated scanning and attacks, potentially affecting a large number of systems rapidly. European organizations with extensive VPN deployments and those relying on strongSwan for inter-site connectivity or remote access are particularly at risk. The absence of known exploits in the wild currently provides a window for proactive mitigation, but the critical severity demands immediate attention.

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #11
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
OWASP Cheat Sheets
Docker Security (opens in a new tab)
XML Security (opens in a new tab)
OWASP ASVS 4.0.3
V5.4.1 (opens in a new tab)
V14.1.2 (opens in a new tab)
V13.3.1 (opens in a new tab)
Attack patterns
Buffer Overflow via Environment Variables (opens in a new tab)
Overflow Buffers (opens in a new tab)
Client-side Injection-induced Buffer Overflow (opens in a new tab)
Filter Failure through Buffer Overflow (opens in a new tab)
MIME Conversion (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Dec 2025, 04:27 UTC

WeaknessesCWE-120

Technical details

References

Community reviews

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