An out‑of‑bounds read occurs in the OpenSSL function X509_VERIFY_PARAM_set1_email when validating the local part of an email address. The bug allows an attacker to supply a specially crafted From: header that bypasses the 64‑octet limit or reads past the buffer. Because the data read is not exposed, the primary consequence is a crash, resulting in a denial of service for any application performing S/MIME validation.

The vulnerability affects any system linking against the OpenSSL library and using S/MIME or X.509 email address validation via X509_VERIFY_PARAM_set1_email. Vendors and product names include OpenSSL OpenSSL. No specific release or version information is provided, so any installation that has not incorporated the patch is potentially vulnerable.

The EPSS score is not available and the issue is not listed in CISA KEV, indicating no known active exploitation. The CVSS score is 6.2, indicating medium severity; the risk is moderate for denial of service. The likely attack vector is network‑based, where an attacker sends a crafted email to a service performing S/MIME validation, causing a crash. Because no data is exfiltrated, the threat is limited to service interruption.