CVE-2026-78133 in strongSwan
Summary
by MITRE • 09/11/2026
libcharon in strongSwan 6.0.0 through 6.0.7 has a use-after-free in IKEv2 rekeying collision handling.
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Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified within the libcharon component of strongSwan versions ranging from 6.0.0 to 6.0.7 represents a critical memory safety flaw specifically located in the logic governing Internet Key Exchange version two, or IKEv2, rekeying collision handling. This issue manifests as a use-after-free error, which is classified under Common Weakness Enumeration identifier CWE-416. The core of this vulnerability lies in how the software manages object lifecycles during concurrent operations where multiple peers attempt to establish or update security associations simultaneously. When such collisions occur, the internal state management fails to properly synchronize access to memory structures that have already been deallocated by another thread or process flow.
In a typical IKEv2 rekeying scenario, an existing Security Association is replaced with a new one while maintaining connectivity. However, when two peers initiate this process concurrently without proper coordination, strongSwan may free the memory associated with an old state structure before all references to that structure have been cleared or transferred. Subsequent operations within the same thread context attempt to access pointers pointing to this freed memory region. Because the operating system has likely repurposed that memory for other allocations, accessing it leads to undefined behavior. This can result in data corruption, application crashes, or potentially allow an attacker with network access to execute arbitrary code by carefully crafting packets that trigger this race condition and manipulate the contents of the reused memory block.
The operational impact of this vulnerability is significant because IKEv2 serves as a foundational protocol for establishing secure tunnels in virtual private networks. An adversary capable of intercepting traffic or acting as a man-in-the-middle could exploit this flaw to destabilize the VPN gateway, causing denial-of-service conditions that disrupt network connectivity for all users relying on the affected strongSwan instance. More severely, if the memory reuse aligns with specific heap layout configurations controlled by the attacker, it may facilitate remote code execution. This compromises not only the integrity of the individual host running strongSwan but also potentially exposes sensitive data transmitted through the established tunnels and undermines trust in the broader network infrastructure protected by these gateways.
Mitigation strategies primarily involve upgrading to a patched version of strongSwan where this race condition has been resolved through improved synchronization mechanisms, such as mutexes or atomic operations, ensuring that memory is only freed when all references are safely nullified. In environments where immediate patching is not feasible, network-level controls should be implemented to restrict IKEv2 traffic sources and monitor for anomalous rekeying patterns that might indicate exploitation attempts. Additionally, enabling Address Sanitizer during development builds can help detect similar issues in future code changes, while adhering to secure coding practices regarding dynamic memory management remains essential to prevent recurrence of CWE-416 type flaws across the software supply chain.