CVE-2026-78134 in strongSwan
Summary
by MITRE • 09/11/2026
strongSwan 4.5.0 through 6.0.7 has Incorrect Access Control in the eap-ttls and eap-peap plugins because there can be a missing or mismatched inner EAP identity.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/11/2026
The vulnerability identified in strongSwan versions ranging from 4.5.0 to 6.0.7 represents a critical flaw within the implementation of Extensible Authentication Protocol (EAP) methods, specifically affecting the eap-ttls and eap-peap plugins. These protocols are widely utilized for establishing secure wireless network access and virtual private network connections by encapsulating authentication credentials inside an encrypted tunnel. The core technical deficiency lies in the handling of inner EAP identities during the authentication handshake process. In a correctly implemented scenario, the server must validate that the identity presented within the tunneled session matches expected criteria or is consistent with outer layer parameters to prevent confusion attacks and ensure proper policy enforcement. However, due to incorrect access control logic, strongSwan fails to adequately verify or enforce constraints on this inner EAP identity. This oversight allows for scenarios where a missing identity or a mismatched identity can bypass intended security checks, effectively weakening the integrity of the authentication mechanism.
From an operational perspective, this flaw creates significant risks related to unauthorized access and session hijacking. An attacker capable of intercepting network traffic could exploit the lack of strict validation on inner identities to perform man-in-the-middle attacks or impersonate legitimate users if combined with other weaknesses in certificate handling or key exchange processes. The absence of proper checks means that authentication decisions may be made based on incomplete or ambiguous identity information, potentially allowing malicious entities to gain access to protected resources without providing valid credentials. This is particularly dangerous in enterprise environments where strongSwan serves as the primary gateway for remote workers or IoT devices relying on EAP-based authentication protocols like PEAP and TTLS for network entry.
This vulnerability aligns with CWE-284, which describes Improper Access Control, specifically relating to insufficient validation of inputs that determine authorization decisions. Furthermore, it relates to ATT&CK technique T1078, Valid Accounts, as the flaw could potentially be leveraged by attackers to use valid but improperly validated credentials or identities to maintain persistent access within a network infrastructure. The root cause is not necessarily a buffer overflow or code injection, but rather a logical error in the state machine and policy enforcement engine of the EAP plugins where identity attributes are processed without sufficient rigor.
Mitigation strategies for this vulnerability primarily involve upgrading strongSwan to versions released after 6.0.7, where these access control checks have been corrected. Organizations relying on affected versions should also implement network-level monitoring to detect anomalous authentication patterns that might indicate exploitation attempts. Additionally, administrators should ensure that EAP configurations strictly enforce identity validation policies and consider supplementing with additional layers of security such as multi-factor authentication or certificate pinning to reduce reliance solely on the inner identity verification mechanism within strongSwan itself until patches are applied.