strongSwan versions 4.5.0 prior to 6.0.5 contain an integer underflow vulnerability in the EAP-TTLS AVP parser that allows unauthenticated remote attackers to cause a denial of service by sending crafted AVP data with invalid length fields during IKEv2 authentication. Attackers can exploit the failure to validate AVP length fields before subtraction to trigger excessive memory allocation or NULL pointer dereference, crashing the charon IKE daemon.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
References 4
https://www.strongswan.org/blog/2026/03/23/strongswan-6.0.5-released.html
disclosure@vulncheck.com
https://www.strongswan.org/blog/2026/03/23/strongswan-vulnerability-(cve-2026-2…
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/strongswan-eap-ttls-avp-parsing-integer-un…
disclosure@vulncheck.com
https://lists.debian.org/debian-lts-announce/2026/03/msg00016.html
af854a3a-2127-422b-91ae-364da2661108