CVE-2026-42771 — MEDIUM (6.2)

Vulnerability 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.

CVSS Score

6.2

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

LOCAL

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

HIGH

Affected Products

Vendor	Product	Versions
Openssl	Openssl	4.0.0

Related Weaknesses (CWE)

CWE-125

References

FAQ

What is CVE-2026-42771?

CVE-2026-42771 is a vulnerability with a CVSS score of 6.2 (MEDIUM). 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. Impa...

How severe is CVE-2026-42771?

CVE-2026-42771 has been rated MEDIUM with a CVSS base score of 6.2/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-42771?

Check the references section above for vendor advisories and patch information. Affected products include: Openssl Openssl.