CRLF injection in NGINX Plus and NGINX Open Source - CVE-2026-28753

Vulnerability identifier: #VU124482

CSH Severity: Medium

CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N]

CVE-ID: CVE-2026-28753

CWE-ID: CWE-93

Exploitation vector: Remote access

Exploit availability: No public exploit available

The vulnerability allows a remote attacker to inject arbitrary data in server response.

The vulnerability exists due to insufficient validation of attacker-supplied data in the ngx_mail_smtp_module module when handling DNS responses. A remote attacker can inject arbitrary headers into SMTP upstream requests and manipulate data.

NGINX Plus
NGINX Open Source
SUSE Linux Enterprise Server 15 SP5
SUSE Linux Enterprise Server 15 SP4
SUSE Linux Enterprise Server 15 SP6
SUSE Linux Enterprise High Performance Computing ESPOS 15
SUSE Linux Enterprise Server for SAP Applications 15
SUSE Linux Enterprise Server 15
SUSE Linux Enterprise High Performance Computing 15
SUSE Linux Enterprise High Performance Computing LTSS 15
SUSE Linux Enterprise Real Time 15
Ubuntu
Server Applications Module
openSUSE Leap
openEuler
Fedora
nginx-mod-vts
nginx-mod-fancyindex
nginx-mod-headers-more
nginx-mod-brotli
nginx-mod-modsecurity
nginx (Ubuntu package)
nginx-mod-naxsi
nginx-debuginfo
nginx
nginx-debugsource
nginx-source
nginx-help
nginx-filesystem
nginx-all-modules
nginx-mod-stream
nginx-mod-mail
nginx-mod-http-xslt-filter
nginx-mod-http-perl
nginx-mod-http-image-filter
nginx-mod-devel

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-debuginfo - addressed in versions 1.21.5-150400.3.15.1, 1.21.5-150600.10.15.1
nginx - addressed in versions 1.21.5-150400.3.15.1, 1.21.5-150600.10.15.1
nginx-debugsource - addressed in versions 1.21.5-150400.3.15.1, 1.21.5-150600.10.15.1
nginx-source - addressed in versions 1.21.5-150400.3.15.1, 1.21.5-150600.10.15.1
nginx - update to 1.24.0-8
nginx-help - update to 1.24.0-8
nginx-filesystem - update to 1.24.0-8
nginx-all-modules - update to 1.24.0-8
nginx-mod-stream - update to 1.24.0-8
nginx-mod-mail - update to 1.24.0-8
nginx-mod-http-xslt-filter - update to 1.24.0-8
nginx-mod-http-perl - update to 1.24.0-8
nginx-mod-http-image-filter - update to 1.24.0-8
nginx-mod-devel - update to 1.24.0-8
nginx-debugsource - update to 1.24.0-8
nginx-debuginfo - update to 1.24.0-8
nginx - update to 1.28.3-1.fc44

• https://my.f5.com/manage/s/article/K000160367

• 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
• openEuler update for nginx
• SUSE update for nginx
• SUSE update for nginx
• Ubuntu update for nginx