FreeS/WAN 1.x and 2.x, and other related products including superfreeswan 1.x, openswan 1.x before 1.0.6, openswan 2.x before 2.1.4, and strongSwan before 2.1.3, allows remote attackers to authenticate using spoofed PKCS#7 certificates in which a self-signed certificate identifies an alternate Certificate Authority (CA) and spoofed issuer and subject.

A flaw was found in the strongSwan payload handling code. This flaw can be triggered by an IKEv1 or IKEv2 message that contains payloads that are only defined for the respective other IKE version. For instance, sending an IKEv1 Main Mode message containing a payload with type 41 (IKEv2 Notify) will crash the daemon or, potentially allow for remote code execution, when a short summary of the contents of the message is logged ("parsed IDPROT request 0 [ ... ]").

strongSwan 5.9.8 and 5.9.9 potentially allows remote code execution because it uses a variable named "public" for two different purposes within the same function. There is initially incorrect access control, later followed by an expired pointer dereference. One attack vector is sending an untrusted client certificate during EAP-TLS. A server is affected only if it loads plugins that implement TLS-based EAP methods (EAP-TLS, EAP-TTLS, EAP-PEAP, or EAP-TNC). This is fixed in 5.9.10.

strongSwan before 5.9.12 has a buffer overflow and possible unauthenticated remote code execution via a DH public value that exceeds the internal buffer in charon-tkm's DH proxy. The earliest affected version is 5.3.0. An attack can occur via a crafted IKESAINIT message.

In strongSwan before 5.9.5, a malicious responder can send an EAP-Success message too early without actually authenticating the client and (in the case of EAP methods with mutual authentication and EAP-only authentication for IKEv2) even without server authentication.

strongMan is a management interface for strongSwan, an OpenSource IPsec-based VPN. When storing credentials in the database (private keys, EAP secrets), strongMan encrypts the corresponding database fields. So far it used AES in CTR mode with a global database key. Together with an initialization vector (IV), a key stream is generated to encrypt the data in the database fields. But because strongMan did not generate individual IVs, every database field was encrypted using the same key stream. An attacker that has access to the database can use this to recover the encrypted credentials. In particular, because certificates, which have to be considered public information, are also encrypted using the same mechanism, an attacker can directly recover a large chunk of the key stream, which allows them to decrypt basically all other secrets especially ECDSA private keys and EAP secrets, which are usually a lot shorter. Version 0.2.0 fixes the issue by switching to AES-GCM-SIV encryption with a random nonce and an individually derived encryption key, using HKDF, for each encrypted value. Database migrations are provided to automatically re-encrypt all credentials.

strongSwan 4.5.0 < 6.0.5 EAP-TTLS AVP Parsing Integer Underflow

In the eap-mschapv2 plugin (client-side) in strongSwan before 6.0.3, a malicious EAP-MSCHAPv2 server can send a crafted message of size 6 through 8, and cause an integer underflow that potentially results in a heap-based buffer overflow.

strongSwan versions 5.9.2 through 5.9.5 are affected by authorization bypass through improper validation of certificate with host mismatch (CWE-297). When certificates are used to authenticate clients in TLS-based EAP methods, the IKE or EAP identity supplied by a client is not enforced to be contained in the client's certificate. So clients can authenticate with any trusted certificate and claim an arbitrary IKE/EAP identity as their own. This is problematic if the identity is used to make policy decisions. A fix was released in strongSwan version 5.9.6 in August 2022 (e4b4aabc4996fc61c37deab7858d07bc4d220136).

The GMP Plugin in strongSwan 4.2.0 through 4.6.3 allows remote attackers to bypass authentication via a (1) empty or (2) zeroed RSA signature, aka "RSA signature verification vulnerability."

The gmp plugin in strongSwan before 5.9.4 has a remote integer overflow via a crafted certificate with an RSASSA-PSS signature. For example, this can be triggered by an unrelated self-signed CA certificate sent by an initiator. Remote code execution cannot occur.

The in-memory certificate cache in strongSwan before 5.9.4 has a remote integer overflow upon receiving many requests with different certificates to fill the cache and later trigger the replacement of cache entries. The code attempts to select a less-often-used cache entry by means of a random number generator, but this is not done correctly. Remote code execution might be a slight possibility.

Last updated 25 August 2025

The gmp plugin in strongSwan before 5.6.0 allows remote attackers to cause a denial of service (NULL pointer dereference and daemon crash) via a crafted RSA signature.

The IKE daemon in strongSwan 4.3.x before 4.3.7 and 4.4.x before 4.4.1 does not properly check the return values of snprintf calls, which allows remote attackers to execute arbitrary code via crafted (1) certificate or (2) identity data that triggers buffer overflows.

Last updated 25 August 2025

In verifyemsapkcs1signature() in gmprsapublickey.c in the gmp plugin in strongSwan 4.x and 5.x before 5.7.0, the RSA implementation based on GMP does not reject excess data in the digestAlgorithm.parameters field during PKCS#1 v1.5 signature verification. Consequently, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation when only an RSA signature is used for IKEv2 authentication. This is a variant of CVE-2006-4790 and CVE-2014-1568.

In verifyemsapkcs1signature() in gmprsapublickey.c in the gmp plugin in strongSwan 4.x and 5.x before 5.7.0, the RSA implementation based on GMP does not reject excess data after the encoded algorithm OID during PKCS#1 v1.5 signature verification. Similar to the flaw in the same version of strongSwan regarding digestAlgorithm.parameters, a remote attacker can forge signatures when small public exponents are being used, which could lead to impersonation when only an RSA signature is used for IKEv2 authentication.

The ASN.1 parser in strongSwan before 5.5.3 improperly handles CHOICE types when the x509 plugin is enabled, which allows remote attackers to cause a denial of service (infinite loop) via a crafted certificate.

The gmp plugin in strongSwan before 5.5.3 does not properly validate RSA public keys before calling mpzpowmsec, which allows remote peers to cause a denial of service (floating point exception and process crash) via a crafted certificate.

strongSwan before 5.9.8 allows remote attackers to cause a denial of service in the revocation plugin by sending a crafted end-entity (and intermediate CA) certificate that contains a CRL/OCSP URL that points to a server (under the attacker's control) that doesn't properly respond but (for example) just does nothing after the initial TCP handshake, or sends an excessive amount of application data.

In TRENDnet TEW-WLC100P 2.03b03, the idontcareaboutsecurityanduseaggressivemodepsk option is enabled in the strongSwan configuration file, so that IKE Responders are allowed to use IKEv1 Aggressive Mode with Pre-Shared Keys to conduct offline attacks on the openly transmitted hash of the PSK.

Paul Wouters reports:

An audit of code from The Libreswan Project revealed a remote buffer overflow in the atodn() function used by both libreswan, openswan, and older versions of strongswan and superfreeswan when called from atoid()

Vulnerable versions: Openswan versions 1.x to 2.6.38

Vulnerability information: When enabling Opportunistic Encryption ("OE") using oe=yes (default is 'no') the IKE daemon pluto requests DNS TXT records to obtain public RSA keys of itself and its peers. These records can contain an IPsec gateway specification containing an fully qualified hostname which is passed to a function atoid().

When X.509 support was added to FreeS/WAN, ASN.1 parsing was added to the function atoid() which converts an ASCII ID representation into an internal struct id representation using a static buffer via the function temporarycyclicbuffer()

While DNS TXT records cannot contain ASN.1 representations, the code mistakenly checked for such interpretation if the DNS TXT FQDN contained an '=' symbol. Since DNS TXT buffers can be larger than what the ASN.1 parsing code expected, parsing such a record can trigger a buffer overflow leading to remote execution of code, specifically when overflowing into the struct kernelops which is a table of function pointers.

Exploitation: This exploit can only be triggered when the ipsec.conf configuration file enables Opportunistic Encryption via the option 'oe=yes'. If this option is not present, it defaults to 'no'.

Configurations that enable "OE" without preconfiguring their own public RSA key in DNS will be under severe connectivity problems leaving the machine with 30 second delay for each outgoing connection - a deployment scenario that is extremely unlikely to appear in the wild.

In the unlikely event that machines are configured as such, this vulnerability can only be exploited by a remote attacker controlling the reverse DNS entry for the IP address of the targetted host. If the machine is properly configured for OE, an attacker only needs to trigger a connection to an IP address for which they control the reverse DNS zone where they can place the malicious DNS record.

Credits: This vulnerability was found by Florian Weimer of the Red Hat Product Security Team (https://access.redhat.com/security/team/)

In strokesocket.c in strongSwan before 5.6.3, a missing packet length check could allow a buffer underflow, which may lead to resource exhaustion and denial of service while reading from the socket.

IKEv2 in strongSwan 4.0.7 before 5.1.3 allows remote attackers to bypass authentication by rekeying an IKESA during (1) initiation or (2) re-authentication, which triggers the IKESA state to be set to established.

A vulnerability was found in Ruijie EG306MG 3.0(1)B11P309. It has been rated as problematic. This issue affects some unknown processing of the file /etc/strongswan.conf of the component strongSwan. The manipulation of the argument idontcareaboutsecurityanduseaggressivemodepsk leads to missing encryption of sensitive data. The attack may be initiated remotely. The complexity of an attack is rather high. The exploitation is known to be difficult. The vendor was contacted early about this disclosure but did not respond in any way.

The rsapssparamsparse function in libstrongswan/credentials/keys/signatureparams.c in strongSwan 5.6.1 allows remote attackers to cause a denial of service via a crafted RSASSA-PSS signature that lacks a mask generation function parameter.

Buffer overflow in the atodn function in strongSwan 2.0.0 through 4.3.4, when Opportunistic Encryption is enabled and an RSA key is being used, allows remote attackers to cause a denial of service (pluto IKE daemon crash) and possibly execute arbitrary code via crafted DNS TXT records. NOTE: this might be the same vulnerability as CVE-2013-2053 and CVE-2013-2054.

The asn1length function in strongSwan 2.8 before 2.8.11, 4.2 before 4.2.17, and 4.3 before 4.3.3 does not properly handle X.509 certificates with crafted Relative Distinguished Names (RDNs), which allows remote attackers to cause a denial of service (pluto IKE daemon crash) via malformed ASN.1 data. NOTE: this is due to an incomplete fix for CVE-2009-2185.

strongSwan 5.0.2 through 5.1.0 allows remote attackers to cause a denial of service (NULL pointer dereference and charon daemon crash) via a crafted IKEv1 fragmentation packet.