Out-of-bounds Read in OpenSSL

CVE-2026-42771

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.

Vulnerability class: Buffer Overflow

Published · last modified .

CVSS v3 metric

CVSS v3 base score 6.2 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.002 (4.5th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 5th percentile — 4.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42771: held from 0.002 to 0.002.

EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: -0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-42771?
CVE-2026-42771 is a medium-severity vulnerability in OpenSSL, classified under Out-of-bounds Read. CVSS score: 6.2/10. Published 2026-06-09.
How severe is CVE-2026-42771?
Medium severity. CVSS v3 base score is 6.2 out of 10.