Double Free Affecting openssl package, versions <3.0.5-2ubuntu2.1

Note: Versions mentioned in the description apply only to the upstream openssl package and not the openssl package as distributed by Ubuntu. See How to fix? for Ubuntu:22.10 relevant fixed versions and status.

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.

• http://people.ubuntu.com/~ubuntu-security/cve/CVE-2022-4450
• https://www.openssl.org/news/secadv/20230207.txt
• https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=63bcf189be73a9cc1264059bed6f57974be74a83
• https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=bbcf509bd046b34cca19c766bbddc31683d0858b
• https://security.gentoo.org/glsa/202402-08