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Fencer Vulns
low 3.7

CVE-2026-28753 json

NGINX ngx_mail_proxy_module vulnerability

published 2026-03-24 7 mo ago modified 2026-09-08 2 mo ago also BIT-nginx-2026-28753 , BIT-nginx-gateway-2026-28753 , EUVD-2026-14885

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 20%
public exploits
0
none known

Summary

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_mail_smtp_module module due to the improper handling of CRLF sequences in DNS responses. This allows an attacker-controlled DNS server to inject arbitrary headers into SMTP upstream requests, leading to potential request manipulation. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Patch / fix

  • bitnami nginx 1.28.3, 1.29.7
  • bitnami nginx-gateway 1.28.3, 1.29.7
  • F5 NGINX Open Source 1.28.3, 1.29.7
  • F5 NGINX Plus R32 P5, R35 P2, R36 P3
  • nginx Debian 12 1.22.1-9+deb12u5
  • nginx Debian 13 1.26.3-3+deb13u3
  • nginx Debian 14 1.28.3-1

debian advisories DEBIAN-CVE-2026-28753

  • nginx Ubuntu 22.04 LTS 1.18.0-6ubuntu14.10
  • nginx Ubuntu 24.04 LTS 1.24.0-2ubuntu7.7
  • nginx Ubuntu 25.10 1.28.0-6ubuntu1.2
  • nginx Ubuntu Pro 14.04 LTS 1.4.6-1ubuntu3.9+esm6
  • nginx Ubuntu Pro 16.04 LTS 1.10.3-0ubuntu0.16.04.5+esm7
  • nginx Ubuntu Pro 18.04 LTS 1.14.0-0ubuntu1.11+esm2
  • nginx Ubuntu Pro 20.04 LTS 1.18.0-0ubuntu1.7+esm1

ubuntu advisories UBUNTU-CVE-2026-28753

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx hummingbird 1 1.30.0-1.hum1
  • nginx-core hummingbird 1 1.30.0-1.hum1
  • nginx-mod-mail hummingbird 1 1.30.0-1.hum1
  • nginx-filesystem hummingbird 1 1.30.0-1.hum1
  • nginx-mod-stream hummingbird 1 1.30.0-1.hum1
  • nginx-all-modules hummingbird 1 1.30.0-1.hum1
  • nginx-mod-http-perl hummingbird 1 1.30.0-1.hum1
  • nginx-mod-http-geoip hummingbird 1 1.30.0-1.hum1

red hat advisories RHSA-2026:8346

  • nginx openSUSE Tumbleweed 1.29.7-1.1

opensuse advisories openSUSE-SU-2026:10423-1

  • nginx Alpine 3.24, Alpine 3.23, Alpine 3.22 1.28.3-r0

alpine advisories ALPINE-CVE-2026-28753

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • nginx Azure Linux 3.0 1.28.3-1

azure linux advisories AZL-80780

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-28753 updated cvss 3.7

NGINX: NGINX Plus: NGINX Open Source: NGINX Plus and NGINX Open Source: Request manipulation via header injection in SMTP upstream requests

  • Red Hat Enterprise Linux 8 nginx, nginx-mod-mail, nginx-filesystem, nginx-mod-stream, nginx-all-modules, nginx-mod-http-perl, +2 more Red Hat Enterprise Linux 9 nginx, nginx-core, nginx-mod-mail, nginx-filesystem, nginx-mod-stream, nginx-all-modules, +3 more Red Hat Enterprise Linux 10 nginx
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images nginx 1.30.0-1.hum1, nginx-core 1.30.0-1.hum1, nginx-mod-mail 1.30.0-1.hum1, nginx-filesystem 1.30.0-1.hum1, nginx-mod-stream 1.30.0-1.hum1, nginx-all-modules 1.30.0-1.hum1, +5 more
    fixed: vendor fix RHSA-2026:8346

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
7 mo ago

Exploit prediction

0.27% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 3.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
bitnami nginx
>=0.6.27, <1.28.3
>=1.29.0, <1.29.7
1.28.3
1.29.7
bitnami nginx-gateway
>=0.6.27, <1.28.3
>=1.29.0, <1.29.7
1.28.3
1.29.7

Affected products

  • F5 NGINX Open Source
  • F5 NGINX Plus

Classification

Weakness
  • CWE-93 Improper Neutralization of CRLF Sequences
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.