CVE-2026-42771

/// Technical description

Issue summary: When the X509_VERIFY_PARAM_set1_email is called by an

application to validate a crafted e-mail address, such as during S/MIME

message validation, an out of bounds read can happen.

Impact summary: This out of bounds read will not directly exfiltrate

the data read to the attacker so the most likely result is a crash and

a Denial of Service.

An internal helper function called from X509_VERIFY_PARAM_[set|add]_email()

used a wrong length when validating the local part of an email address.

This could cause the 64 octet limit on the local part of an email address

to be not enforced, or cause an out of bound read and potentially a crash.

The bug is reachable via S-MIME validation with a crafted From: address

supplied in an email message that can potentially cause a crash.

No FIPS modules are affected by this issue as the affected code is outside

the OpenSSL FIPS module boundary.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References