CVE-2026-42771

Issue summary: When the X509VERIFYPARAMset1email 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 X509VERIFYPARAM_[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.

Database specific

{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42771.json",
    "cwe_ids": [
        "CWE-125"
    ],
    "cna_assigner": "openssl"
}

References

Affected packages

Git / github.com/openssl/openssl

Affected ranges

Type

GIT

Repo

https://github.com/openssl/openssl

Events

Introduced

11b7b6ea3b65a584e1d31408ed1bdb139465cffd

Fixed

1e963a8680ec78ad2072792c7a1a71f3c530bd2e

Database specific

{
    "source": "AFFECTED_FIELD",
    "extracted_events": [
        {
            "introduced": "4.0.0"
        },
        {
            "fixed": "4.0.1"
        }
    ]
}

Affected versions

4.*

4.0.0-NA

openssl-4.*

openssl-4.0.0

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42771.json"