Integer Underflow Vulnerability in strongSwan's EAP-TTLS AVP Parser

CVE-2026-25075

What is CVE-2026-25075?

CVE-2026-25075 is a security vulnerability identified in strongSwan, an open-source software suite that provides virtual private network (VPN) solutions and secure communications. This specific issue arises from an integer underflow vulnerability in the EAP-TTLS AVP (Attribute-Value Pair) parser, affecting strongSwan versions from 4.5.0 up to, but not including, 6.0.5. The vulnerability allows unauthenticated remote attackers to exploit a flaw during the IKEv2 authentication process. By sending crafted AVP data with invalid length fields, attackers can cause excessive memory allocation or trigger a NULL pointer dereference, resulting in a denial of service when the charon IKE daemon crashes. This vulnerability underscores the critical need for organizations using strongSwan to maintain updated software to prevent successful exploitation.

Potential impact of CVE-2026-25075

1. Denial of Service: The primary risk associated with CVE-2026-25075 is the potential for denial of service attacks. Exploiting this vulnerability can lead to the crashing of the charon IKE daemon, disrupting VPN services and hindering organizational communications.

2. Unauthenticated Remote Access: Since the vulnerability can be triggered by unauthenticated remote attackers, there is a concerning vector for malicious actors to exploit the system without requiring prior access. This can lead to broader attacks against the network infrastructure of the organization.

3. Increased Attack Surface: With the potential to leverage this vulnerability in conjunction with other threats, it increases the attack surface of affected systems, rendering organizations more susceptible to compounded security issues and potentially leading to further exploits in the future.

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