The function 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 PEM_read_bio_ex() 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.
The functions PEM_read_bio() and 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 functions including PEM_X509_INFO_read_bio_ex() and 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 include the PEM_read_bio_TYPE() functions as well as the decoders introduced in OpenSSL 3.0.
The OpenSSL asn1parse command line application is also impacted by this issue.
The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Openssl | Openssl | 1.1.1 (including) | 1.1.1t (excluding) |
| Openssl | Openssl | 3.0.0 (including) | 3.0.8 (excluding) |