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High severity · published Mar 24, 2026
CVE-2026-27651
NGINX ngx_mail_auth_http_module vulnerability
7.5
CVSS
1%
EPSS
No
On KEV
Description
When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.0% · higher than 61% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NO
NGINX Open Source · F5
1.29.0 before 1.29.7; 0.5.15 before 1.28.3 · source: vendor, NVD
NP
NGINX Plus · F5
R36 before R36 P3; R35 before R35 P2; R34; R33; R32 before R32 P5 · source: vendor, NVD
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9.0 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9.4 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9.6 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Hardened Images · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Update Infrastructure 5 · Red Hat
All versions, or not specified · source: CISA
Affected product
NO
NGINX Open Source
F5
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-27651
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-27651
Vendor Advisory
https://my.f5.com/manage/s/article/K000160383
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:10065
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:13634
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:13680
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:13839
access.redhat.com
https://access.redhat.com/errata/RHSA-2026:14836
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