RUSTSEC-2023-0010: Double free after calling `PEM_read_bio_ex`

What to do

1. See which version you have: cargo tree -i openssl-src (it also shows which of your dependencies pulls it in).
2. Update within your version requirement: cargo update -p openssl-src. If the fix is a newer major or minor than your requirement allows, raise it in Cargo.toml (for example openssl-src = "300.0.12") or update the dependency that pulls it in.
3. Check again with cargo audit, or paste your Cargo.lock into our Cargo.toml checker.

Details from the advisory

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.

References

• Package: crates.io/crates/openssl-src
• Advisory: rustsec.org/advisories/RUSTSEC-2023-0010.html
• Web: www.openssl.org/news/secadv/20230207.txt

From the RustSec Advisory Database (CC0-1.0) via the OSV export, downloaded Oct 24, 2026. Severity score computed from the published CVSS vector.

Other advisories for openssl-src

• Vulnerability HighRUSTSEC-2020-0015 · 2020-04-25Crash causing Denial of Service attack
• Vulnerability MediumRUSTSEC-2021-0055 · 2021-05-01NULL pointer deref in signature_algorithms processing
• Vulnerability HighRUSTSEC-2021-0056 · 2021-05-01CA certificate check bypass with X509_V_FLAG_X509_STRICT
• Vulnerability HighRUSTSEC-2021-0057 · 2021-05-01Integer overflow in CipherUpdate
• Vulnerability MediumRUSTSEC-2021-0058 · 2021-05-01Null pointer deref in `X509_issuer_and_serial_hash()`
• Vulnerability CriticalRUSTSEC-2021-0097 · 2021-08-24SM2 Decryption Buffer Overflow
• Vulnerability HighRUSTSEC-2021-0098 · 2021-08-24Read buffer overruns processing ASN.1 strings
• VulnerabilityRUSTSEC-2021-0129 · 2021-12-14Invalid handling of `X509_verify_cert()` internal errors in libssl

Full security history of openssl-src