Overview
About vulnerability
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.
Details
- Affected product:
- AlmaLinux 9.2 ESU , Alpine Linux 3.22 , CentOS 8.4 ELS , CentOS 8.5 ELS , Debian 10 , Debian 10 ELS , Debian 11 , Debian 12 , Debian 13 , EL 10 , EL 7 , EL 8 , EL 9 , Ubuntu 16.04 , Ubuntu 18.04 , Ubuntu 18.04 ELS , Ubuntu 20.04 , Ubuntu 22.04 , Ubuntu 24.04
- Affected packages:
- openssl @ 3.0.7-20 (+19 more)
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.