CVE-2026-2673 OpenSSL TLS 1.3密钥协商组选择配置缺陷

/* * CVE-2026-2673 PoC - OpenSSL TLS 1.3 Key Exchange Group Selection Issue * This PoC demonstrates the vulnerability where using 'DEFAULT' keyword * causes loss of tuple structure, preventing proper post-quantum group negotiation. * * Build: gcc -o cve2026_poc cve2026_poc.c -lssl -lcrypto * Run: ./cve2026_poc <server_ip> <port> */ #include <stdio.h> #include <string.h> #include <openssl/ssl.h> #include <openssl/err.h> #define TARGET_HOST argv[1] #define TARGET_PORT argv[2] void print_tls_groups(SSL *ssl) { const char *groups = SSL_get0_peer_supported_groups(ssl); if (groups) { printf("[*] Server supported groups: %s\n", groups); } /* Check if post-quantum groups are available */ if (strstr(groups, "X25519MLKEM768") != NULL) { printf("[!] Server supports X25519MLKEM768 but may not negotiate it properly\n"); } } int main(int argc, char **argv) { SSL_CTX *ctx; SSL *ssl; BIO *bio; if (argc < 3) { printf("Usage: %s <host> <port>\n", argv[0]); return 1; } /* Initialize OpenSSL */ SSL_library_init(); SSL_load_error_strings(); OpenSSL_add_all_algorithms(); /* Create SSL context for TLS 1.3 client */ ctx = SSL_CTX_new(TLS_client_method()); SSL_CTX_set_min_proto_version(ctx, TLS1_3_VERSION); SSL_CTX_set_max_proto_version(ctx, TLS1_3_VERSION); /* Configure to request post-quantum hybrid groups */ SSL_CTX_set1_groups_list(ctx, "X25519MLKEM768:P-256"); /* Create SSL connection */ ssl = SSL_new(ctx); bio = BIO_new_ssl_connect(ctx); BIO_set_conn_hostname(bio, TARGET_HOST ":" TARGET_PORT); SSL_set_bio(ssl, bio, bio); /* Attempt connection */ if (SSL_connect(ssl) <= 0) { printf("[!] Connection failed: %s\n", ERR_error_string(ERR_get_error(), NULL)); return 1; } printf("[*] TLS 1.3 connection established\n"); print_tls_groups(ssl); /* Check negotiated cipher */ const char *cipher = SSL_get_cipher(ssl); printf("[*] Negotiated cipher: %s\n", cipher); /* The vulnerability: even if server supports X25519MLKEM768, * it may negotiate a less secure group due to DEFAULT keyword issue */ if (strstr(cipher, "TLS_AES_256_GCM_SHA384") == NULL) { printf("[!] WARNING: Post-quantum group may not be negotiated properly!\n"); } SSL_shutdown(ssl); SSL_free(ssl); SSL_CTX_free(ctx); return 0; }