PEM_read_bio_ex() reads a PEM file from a BIO and parses and
decodes the "name" (e.g. "CERTIFICATE"), any header data and the payload data.
If the function succeeds then the "name_out", "header" and "data" arguments are
populated with pointers to buffers containing the relevant decoded data. The
caller is responsible for freeing those buffers. It is possible to construct a
PEM file that results in 0 bytes of payload data. In this case
will return a failure code but will populate the header argument with a pointer
to a buffer that has already been freed. If the caller also frees this buffer
then a double free will occur. This will most likely lead to a crash. This
could be exploited by an attacker who has the ability to supply malicious PEM
files for parsing to achieve a denial of service attack.
PEM_read() are simple wrappers around
PEM_read_bio_ex() and therefore these functions are also directly affected.
These functions are also called indirectly by a number of other OpenSSL
SSL_CTX_use_serverinfo_file() which are also vulnerable. Some OpenSSL internal
uses of these functions are not vulnerable because the caller does not free the
header argument if
PEM_read_bio_ex() returns a failure code. These locations
PEM_read_bio_TYPE() functions as well as the decoders introduced in