CVE-2026-42771
CWE-125Published: June 9, 2026· Updated: Jun 16, 2026
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.
Technical Analysis
CVE-2026-42771 requires local access, meaning attackers must already have a foothold on the target system.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 6.2.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (2)
Quick Facts
Related CVEs (CWE-125)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2026-42771 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts