High severity · published May 26, 2026
CVE-2026-42013
Gnutls: gnutls: certificate validation bypass due to oversized subject alternative name
8.2
CVSS
0.4%
EPSS
No
On KEV
Description
A flaw was found in gnutls. When validating certificates, an oversized Subject Alternative Name (SAN) could cause the validation process to incorrectly fall back to checking the Common Name (CN) field. This could allow a remote attacker to bypass proper certificate validation, potentially leading to spoofing or man-in-the-middle attacks.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 36% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
CM
Cert Manager support for Red Hat OpenShift release 1.17 · Red Hat
All versions, or not specified · source: vendor
CM
Cert Manager support for Red Hat OpenShift release 1.18 · Red Hat
All versions, or not specified · source: vendor
CM
Cert Manager support for Red Hat OpenShift release 1.20 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Discovery 2 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 6 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 7 Extended Lifecycle Support · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On · Red Hat
All versions, or not specified · source: vendor
RH
Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support · Red Hat
All versions, or not specified · source: vendor
Affected product
CM
Cert Manager support for Red Hat OpenShift release 1.17
Red Hat
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42013
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-42013
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:13274
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:20611
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:20612
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:20613
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26319
vendor-advisory
https://access.redhat.com/errata/RHSA-2026:26409
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