Medium severity · published Jun 9, 2026
CVE-2026-42771
Possible Out of Bounds Read in X509_VERIFY_PARAM_set1_email()
6.2
CVSS
0.2%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Local
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 12% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
OP
OpenSSL · OpenSSL
4.0.0 before 4.0.1 · source: vendor, NVD
In the news
VulnerabilityHigh
ZDI-26-426: OpenSSL X.509 Email Validation Out-Of-Bounds Read Information Disclosure Vulnerability
This vulnerability allows remote attackers to disclose sensitive information on affected installations of OpenSSL. Authentication is not required to exploit this vulnerability. The ZDI has assigned a CVSS rating of 6.5. The following CVEs are assigned: CVE-2026-42771.
Jul 15, 2026·Zero Day Initiative
Affected product
OP
OpenSSL
OpenSSL
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