CVE-2022-4450

A double-free vulnerability was found in OpenSSL's PEM_read_bio_ex function. The function PEM_read_bio_ex() reads a PEM file from a BIO and parses and decodes the "name" (for example, "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. Constructing a PEM file that results in 0 bytes of payload data is possible. In this case, PEM_read_bio_ex() will return a failure code but will populate the header argument with a pointer to a freed buffer. A double-free will occur if the caller also frees this buffer. This will most likely lead to a crash. This could be exploited by an attacker who can supply malicious PEM files for parsing to achieve a denial of service attack.

A double-free vulnerability was found in the OpenSSL library in the PEM_read_bio_ex() function and its wrappers. The flaw is triggered when the library parses a specially crafted PEM file constructed to have zero bytes of payload data. This edge case causes the function to return a failure code but also populate a header argument with a pointer to memory that has already been freed, leading to a double-free condition if the calling application also attempts to free it, resulting in a crash and a denial of service. The flaw is rated as moderate because it results in a crash but does not allow code execution, memory corruption beyond the crash, or data leakage.

The versions of shim as shipped with Red Hat Enterprise Linux 8 and 9 are shipping OpenSSL 1.1.1 and 1.0.2, which do not contain the incorrect code, so those are not affected by this CVE.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.