Updating a column in one table based on matches with column in another table
You can try something like this, this is setting table1's col3 value to table2's col3 value where they match on col1 and col2. You can replace the col3 with your 'some value'.

create table table1 (
col1 int,
col2 int,
col3 int
);

create table table2 (
col1 int,  
col2 int,
col3 int
);

insert into table1 values (1,2,3);
insert into table1 values (4,5,6);

insert into table2 values (1,2,10);
insert into table2 values (4,5,20);

select * from table1;

update table1
set col3 = (
 select table2.col3
  from table2
 where table1.col1 = table2.col1
   and table1.col2 = table2.col2
)
where exists (
select table2.col3
  from table2
 where table1.col1 = table2.col1
   and table1.col2 = table2.col2
);

select * from table1;


DB Fiddle