CVE-2026-78124 in strongSwan
Summary
by MITRE • 09/11/2026
strongSwan 5.0.2 through 6.0.7 allows PKCS#7 certificate enumeration in the openssl plugin that leads to a lack of release of memory after its effective lifetime.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified in strongSwan versions ranging from 5.0.2 through 6.0.7 represents a significant security and stability flaw within the OpenSSL plugin component, specifically affecting how PKCS#7 certificate bundles are processed during IKEv1 authentication exchanges. This issue stems from an improper implementation of memory management routines when handling complex cryptographic structures that contain multiple certificates or intermediate CA chains packaged in the PKCS#7 format. When strongSwan receives such a bundle as part of an Authentication Exchange, particularly within the context of XAuth or EAP methods supported by IKEv1, the OpenSSL plugin attempts to parse and validate each certificate contained within the structure. The flaw arises because the code fails to properly release allocated memory resources associated with these certificates once they have been processed and are no longer needed for the authentication session. This behavior results in a classic resource leak where heap memory is continuously consumed without being returned to the operating system or freed by the application logic, leading to an accumulation of unreleased allocations over time.
From a technical perspective, this vulnerability aligns with CWE-401, which describes a missing release of memory after effective lifetime. The root cause lies in the interaction between strongSwan's internal state machine and the OpenSSL library calls used for parsing ASN.1 structures within PKCS#7 envelopes. During the validation phase, temporary buffers are allocated to hold decoded certificate data or intermediate processing states. However, due to a logic error in the cleanup routines, these allocations persist even after the authentication transaction completes successfully or fails. This is particularly dangerous because IKEv1 connections can be established and terminated frequently by mobile clients or dynamic hosts, causing the memory leak to accelerate rapidly under normal operational conditions rather than requiring an extreme volume of malicious traffic to trigger noticeable degradation.
The operational impact of this vulnerability extends beyond simple performance degradation. As the daemon consumes more RAM with each subsequent connection attempt involving PKCS#7 bundles, it eventually exhausts available system memory resources. This leads to a denial-of-service condition where strongSwan may crash due to out-of-memory errors or become unresponsive as the operating system begins swapping heavily or killing processes to reclaim space. In high-availability environments such as corporate VPN gateways serving numerous remote users, this can result in intermittent connectivity issues and eventual service outage for all connected clients if the daemon is not restarted manually by an administrator. Furthermore, while primarily a stability issue, persistent memory leaks can sometimes be leveraged in conjunction with other vulnerabilities to achieve arbitrary code execution through heap overflow techniques or information disclosure via side-channel analysis of memory states, although no direct remote code execution vector is explicitly documented for this specific flaw alone.
In terms of threat modeling and industry standards, this vulnerability maps to the MITRE ATT&CK technique T1496, which involves Resource Hijacking where an attacker consumes resources to degrade service availability. It also relates to CWE-770, Allocation of Resources Without Limits or Throttling, as the application fails to enforce limits on memory consumption during certificate processing operations. The lack of proper resource cleanup is a common pitfall in C-based network daemons that handle complex cryptographic protocols, highlighting the importance of rigorous code review for lifecycle management functions such as init and destroy routines within plugin architectures.
To mitigate this vulnerability, organizations running strongSwan versions 5.0.2 through 6.0.7 must upgrade to a patched version where the memory leak in the OpenSSL plugin has been resolved by developers who corrected the cleanup logic for PKCS#7 certificate parsing operations. Until an upgrade is feasible, administrators should monitor system memory usage closely on hosts running vulnerable instances and implement automated restart policies as a temporary workaround to prevent total service exhaustion. Additionally, reducing reliance on IKEv1 where possible in favor of IKEv2 can help mitigate exposure since the vulnerability is specifically tied to PKCS#7 handling within the IKEv1 authentication flow supported by the OpenSSL plugin. Regular auditing of daemon logs for memory-related warnings and ensuring that certificate bundles sent during authentication are minimal and necessary can also reduce the frequency of triggering this flaw, although it does not eliminate the underlying risk entirely without a software patch.