CVE-2026-77205

Libreswan before 3.18 allows remote attackers to cause a denial of service via NULL pointer dereference, leading to a restart of the pluto daemon.

In libreswan before version 3.17, there is an issue with retransmission in initial responder states, allowing remote attackers to cause a denial of service (traffic amplification) via a spoofed UDP packet.

Libreswan version 3.16 may allow remote attackers to cause a denial of service (daemon restart) via an IKEv2 aes_xcbc transform.

Libreswan's pluto daemon has a use-after-free vulnerability when a client connecting using IKE over TCP closes the connection and another packet (retransmit or malicious) is received for the same tuple. IKE state is retained in memory after the client closes the connection, storing a pointer to iface_endpoint inside ike_sa.sa->st_iface_endpoint. Once this invalid pointer is used, the daemon crashes and restarts. This vulnerability can be triggered before the remote peer has authenticated itself. Continued exploitation can lead to a denial of service. Remote code execution could be possible. The IKE over TCP option is not enabled by default; only configurations that contain listen-tcp=yes are affected.

Libreswan has a null pointer dereference bug in the PKCS#7 handling code for IKE certificate authentication. When libreswan decodes an IKE CERT payload of type CERT_PKCS7_WRAPPED_X509, it guards the PKCS#7 blob with SEC_PKCS7ContainsCertsOrCrls() and then iterates the certificate list with SEC_PKCS7GetCertificateList(). The two NSS APIs disagree on a SignedData that carries a CRL but no certificates: ContainsCertsOrCrls() returns PR_TRUE (there is a CRL), so the guard passes, but GetCertificateList() returns NULL (there are no certificates). This causes libreswan to dereference a null pointer leading to a crash and restart. A malicious IKE_AUTH packet can trigger this bug, meaning the peer does not need to be authenticated. No remote code execution is possible. Continued exploitation can cause a denial of service.

Libreswan's IKEv2 state machine has a null pointer dereference bug in the EAP handling code for authentication. As a result of inconsistency within the IKEv2 state machine code, this bug can be triggered by any IKEv2 connection, even if EAP is not configured at all. The error is caused by a fall-through where it incorrectly dereferences ike->sa.st_eap which is NULL. A malicious IKE_AUTH packet can trigger this bug, meaning the peer does not need to be authenticated. The bug results in a crash and restart of the pluto daemon. No remote code execution is possible. Continued exploitation can cause a denial of service.

In FIPS mode, Libreswan's add_decoded_cert() function calls CERT_ExtractPublicKey() and asserts that the result is not NULL. However, CERT_ExtractPublicKey() returns NULL when public key extraction fails, for example if the RSA exponent is set to 0. A remote attacker can send a malformed X.509 certificate in a CERT payload to trigger the assertion, causing the pluto daemon to abort and restart. Continued exploitation causes a denial of service. No remote code execution is possible. Both IKEv1 and IKEv2 are affected. The vulnerability is only exploitable when both the OS and libreswan are running in FIPS mode and at least one CA certificate is loaded. The CERT payload is processed before peer authentication, so no credentials are needed to exploit this. Configurations using only PreSharedKey (PSK) authentication with no CA certificates loaded in the NSS database are not vulnerable.

In Libreswan, the function RSA_authenticate_hash_signature_pkcs1_1_5_rsa() incorrectly verifies the DER encoding of the ASN.1 digest when the IKEv2 AUTH payload uses RSASSA-PKCS1-v1_5. A remote attacker can exploit a Bleichenbacher-style attack to forge the AUTH payload, leading to impersonation, or trigger an assertion causing denial-of-service.

Libreswan has a vulnerability in the RSA_authenticate_hash_signature_raw_rsa() function that incorrectly verifies the authentication hash length in IKEv1 packets using PKCS #1 RSA encoding. A remote attacker can forge the SIG payload via a Bleichenbacher-style attack, leading to impersonation, or cause denial-of-service by sending a shorter hash.

An invalidly formatted IKEv2 fragment causes the Libreswan pluto daemon to crash and restart. An off-by-one error in the PASSERT assertion leads to daemon abort.