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Fencer Vulns
low 3.7

CVE-2025-53859 json

NGINX ngx_mail_smtp_module vulnerability

published 2025-08-13 14 mo ago modified 2026-09-08 2 mo ago also BIT-nginx-2025-53859 , BIT-nginx-gateway-2025-53859 , EUVD-2025-24579

cvss
3.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 38%
public exploits
0
none known

Summary

NGINX Open Source and NGINX Plus have a vulnerability in the ngx_mail_smtp_module that might allow an unauthenticated attacker to over-read NGINX SMTP authentication process memory; as a result, the server side may leak arbitrary bytes sent in a request to the authentication server. This issue happens during the NGINX SMTP authentication process and requires the attacker to make preparations against the target system to extract the leaked data. The issue affects NGINX only if (1) it is built with the ngx_mail_smtp_module, (2) the smtp_auth directive is configured with method "none," and (3) the authentication server returns the "Auth-Wait" response header.

Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Patch / fix

  • bitnami nginx 1.29.1
  • bitnami nginx-gateway 1.29.1
  • F5 NGINX Plus R32 P3, R33 P3, R34 P2, R35
  • F5 NGINX Open Source 1.29.1
  • nginx Debian 12 1.22.1-9+deb12u3
  • nginx Debian 13 1.26.3-3+deb13u1
  • nginx Debian 14 1.28.0-3

debian advisories DEBIAN-CVE-2025-53859

  • nginx Ubuntu 22.04 LTS 1.18.0-6ubuntu14.7
  • nginx Ubuntu 24.04 LTS 1.24.0-2ubuntu7.5
  • nginx Ubuntu 25.10 1.26.3-3ubuntu3
  • 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-2025-53859

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 1.29.1-1.1

opensuse advisories openSUSE-SU-2025:15449-1

  • nginx Alpine 3.24, Alpine 3.23, Alpine 3.22 1.28.2-r0

alpine advisories ALPINE-CVE-2025-53859

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 CBL-Mariner 2.0 1.22.1-14
  • nginx Azure Linux 3.0 1.25.4-5

azure linux advisories AZL-66308AZL-66311

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-2025-53859 updated cvss 3.7

nginx: NGINX ngx_mail_smtp_module vulnerability

  • 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 Red Hat Lightspeed proxy 1 insights-proxy/insights-proxy-container-rhel9
    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
14 mo ago

Exploit prediction

0.44% chance of exploitation in the next 30 days, higher than 38% 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:L/I:N/A:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/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
>=0.7.0, <1.29.1
1.29.1
bitnami nginx-gateway
>=0.7.0, <1.29.1
1.29.1

Affected products

  • F5 NGINX Plus
  • F5 NGINX Open Source

Classification

Weakness
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.