NULL pointer dereference in NGINX Plus and NGINX Open Source - CVE-2026-27651

Vulnerability identifier: #VU124473

CSH Severity: Medium

CVSS v4: 8.2 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-27651

CWE-ID: CWE-476

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error within the ngx_mail_auth_http_module module. A remote attacker can send specially crafted request to the server and perform a denial of service (DoS) attack.

Successful exploitation of the vulnerability requires that the CRAM-MD5 or APOP authentication is enabled, and the authentication server permits retry by returning the Auth-Wait response header.

NGINX Plus
NGINX Open Source
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise Real Time 15
Red Hat Enterprise Linux for ARM 64
Red Hat Enterprise Linux for Power, little endian
Red Hat Enterprise Linux for IBM z Systems
Red Hat Enterprise Linux for x86_64
Red Hat Enterprise Linux Server - AUS
Red Hat Enterprise Linux for Power, little endian - Extended Update Support
Red Hat Enterprise Linux for ARM 64 - Extended Update Support
Red Hat Enterprise Linux for IBM z Systems - Extended Update Support
Red Hat Enterprise Linux for x86_64 - Extended Update Support
Red Hat CodeReady Linux Builder for ARM 64 - Extended Update Support
Red Hat CodeReady Linux Builder for IBM z Systems - Extended Update Support
Red Hat CodeReady Linux Builder for Power, little endian - Extended Update Support
Red Hat CodeReady Linux Builder for x86_64 - Extended Update Support
Ubuntu
Server Applications Module
openSUSE Leap
openEuler
Anolis OS
Fedora
Red Hat Enterprise Linux Server for Power LE - Update Services for SAP Solutions
nginx-mod-vts
nginx-mod-fancyindex
nginx-mod-headers-more
nginx-mod-brotli
nginx-mod-modsecurity
nginx (Ubuntu package)
nginx-mod-naxsi
nginx (Red Hat package)
nginx-source
nginx-debugsource
nginx
nginx-debuginfo
nginx-filesystem
nginx-mod-devel
nginx-mod-http-image-filter
nginx-mod-http-perl
nginx-mod-http-xslt-filter
nginx-mod-mail
nginx-mod-stream
nginx-help
nginx-all-modules
nginx-doc
nginx-core

Install updates from vendor's website.

NGINX Plus - addressed in versions R32 P5, R35 P2, R36 P3
NGINX Open Source - addressed in versions 1.28.3, 1.29.7
nginx-mod-vts - update to 0.2.4-7.fc44
nginx-mod-fancyindex - update to 0.6.0-2.fc44
nginx-mod-headers-more - update to 0.39-7.fc44
nginx-mod-brotli - update to 1.0.0~rc-7.fc44
nginx-mod-modsecurity - update to 1.0.4-8.fc44
nginx (Ubuntu package) - addressed in versions 1.4.6-1ubuntu3.9+esm6, 1.10.3-0ubuntu0.16.04.5+esm7, 1.14.0-0ubuntu1.11+esm2, 1.18.0-0ubuntu1.7+esm1
nginx-mod-naxsi - update to 1.6-15.fc44
nginx (Red Hat package) - addressed in versions 1.20.1-10.el9_0.3, 1.20.1-14.el9_2.5, 1.20.1-16.el9_4.5, 1.20.1-24.el9_7.2, 1.26.3-1.el10_0.8, 1.26.3-2.el10_1.1
nginx-source - addressed in versions 1.21.5-150400.3.20.1, 1.21.5-150600.10.18.1
nginx-debugsource - addressed in versions 1.21.5-150400.3.20.1, 1.21.5-150600.10.18.1
nginx - addressed in versions 1.21.5-150400.3.20.1, 1.21.5-150600.10.18.1
nginx-debuginfo - addressed in versions 1.21.5-150400.3.20.1, 1.21.5-150600.10.18.1
nginx-filesystem - update to 1.24.0-8
nginx - update to 1.24.0-8
nginx-debuginfo - update to 1.24.0-8
nginx-debugsource - update to 1.24.0-8
nginx-mod-devel - update to 1.24.0-8
nginx-mod-http-image-filter - update to 1.24.0-8
nginx-mod-http-perl - update to 1.24.0-8
nginx-mod-http-xslt-filter - update to 1.24.0-8
nginx-mod-mail - update to 1.24.0-8
nginx-mod-stream - update to 1.24.0-8
nginx-help - update to 1.24.0-8
nginx-all-modules - update to 1.24.0-8
nginx-filesystem - update to 1.26.2-8
nginx-doc - update to 1.26.2-8
nginx-all-modules - update to 1.26.2-8
nginx-mod-stream - update to 1.26.2-8
nginx-mod-mail - update to 1.26.2-8
nginx-mod-http-xslt-filter - update to 1.26.2-8
nginx-mod-http-perl - update to 1.26.2-8
nginx-mod-http-image-filter - update to 1.26.2-8
nginx-mod-devel - update to 1.26.2-8
nginx-core - update to 1.26.2-8
nginx - update to 1.26.2-8
nginx - update to 1.28.3-1.fc44

• https://my.f5.com/manage/s/article/K000160383

• Multiple vulnerabilities in NGINX Open Source and NGINX Plus
• Fedora 44 update for nginx, nginx-mod-brotli, nginx-mod-fancyindex, nginx-mod-headers-more, nginx-mod-modsecurity, nginx-mod-naxsi, nginx-mod-vts
• Red Hat Enterprise Linux 10 update for nginx
• Red Hat Enterprise Linux 8 update for the nginx:1.24 module
• Red Hat Enterprise Linux 9 update for the nginx:1.24 module
• Red Hat Enterprise Linux 9 update for nginx
• Red Hat Enterprise Linux 9 update for the nginx:1.26 module
• openEuler update for nginx
• Anolis OS update for nginx
• Red Hat Enterprise Linux 10 update for nginx
• Red Hat Enterprise Linux 9 update for nginx
• Red Hat Enterprise Linux 9 update for nginx
• Red Hat Enterprise Linux 9 update for nginx
• Red Hat Enterprise Linux 9 update for the nginx:1.24 module
• Red Hat Enterprise Linux 9 update for the nginx:1.24 module
• Red Hat Enterprise Linux 9 update for the nginx:1.26 module
• SUSE update for nginx
• Ubuntu update for nginx
• SUSE update for nginx