Vulnerability · Published Jun 9, 2026 · Assigned by openssl

CVE-2026-42771Possible Out of Bounds Read in X509_VERIFY_PARAM_set1_email()

Medium 6.2

In plain English

A medium-severity out-of-bounds read in OpenSSL from OpenSSL. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities).

Severity (CVSS 3.1)6.2Medium

Exploit odds (30 days)0.2%top 87.7% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
OpenSSL	OpenSSL	4.0.0 – before 4.0.1

Weakness: CWE-125 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

OpenSSL Advisory vendor-advisory
4.0.1 git commit patch