6.3

CVE-2026-28753: f5 nginx open source CRLF Injection

CVSS: 6.3v4.0MediumAnalyzed
AliasesALPINE-CVE-2026-28753UBUNTU-CVE-2026-28753DEBIAN-CVE-2026-28753
Published 24-03-2026Last modified 24-03-2026
Open JSON

Vulnerability summary

CVE-2026-28753 is a medium (CVSS 6.3) CRLF Injection vulnerability in f5 nginx open source. EPSS estimates a 0.26% chance of exploitation in the next 30 days, higher than 17.1% of scored vulnerabilities.

Overall risk
25/100
0100
Medium · default modelHow is this calculated?
CVSS score
6.3/10
010
Medium · v4.0 (CVE.org)
EPSS score
0.26%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 3 · Related 4
MGASA-2026-0111OPENSUSE-SU-2026:10423-1RHSA-2026:8346CGA-X8HQ-W44M-4FH3USN-8210-1USN-8375-1

Timeline

  1. 24-03-2026
    PublishedVulnerability first disclosed.
  2. 24-03-2026
    Last modifiedVulnerability information updated.

Description

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.

CVSS metrics

10 scores · 7 sources · 2 versions

EPSS trend

Probability

0.26%

Chance of exploitation in the next 30 days

Percentile

17%

Versus all other CVEs

30-day change

0.00 pp

From 0.26% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.26%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Chainguard2 products
  • nginx-mainline< 1.29.7-r0
  • nginx-stable< 1.28.3-r0
F52 products
  • nginx open source≥ 0.6.27, < 1.28.3 | ≥ 0.6.27, ≤ 0.9.7 | ≥ 1.0.0, < 1.28.3 | ≥ 1.29.0, < 1.29.7
  • nginx plus≥ R36, < R36 P3 | ≥ R35, < R35 P2 | ≥ R34 (No fix recorded) | ≥ R33 (No fix recorded) | ≥ R32, < R32 P5 | r32:p1 | r32:p2 | r32:p3 | r32:p4 | r33 | r33:p1 | r33:p2 | r33:p3 | r34 | r34:p1 | r34:p2 | r35 | r35:p1 | r36 | r36:p1 | r36:p2
Wolfi2 products
  • nginx-mainline< 1.29.7-r0
  • nginx-stable< 1.28.3-r0
Alpine1 product
  • nginx< 1.28.3-r0
Debian1 product
  • nginx< 1.22.1-9+deb12u5 | < 1.26.3-3+deb13u3 | < 1.28.3-1
Ubuntu1 product
  • nginx< 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 | < 1.18.0-6ubuntu14.10 | < 1.24.0-2ubuntu7.7 | < 1.28.0-6ubuntu1.2

6 vendors · 9 products

References

8 links