Low severity · published Mar 24, 2026
CVE-2026-28753
NGINX ngx_mail_proxy_module vulnerability
3.7
CVSS
0.3%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 20% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NO
NGINX Open Source · F5
1.29.0 before 1.29.7; 0.6.27 before 1.28.3 · source: vendor, NVD
NP
NGINX Plus · F5
R36 before R36 P3; R35 before R35 P2; R34; R33; R32 before R32 P5 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-28753
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-28753
Vendor Advisory
https://my.f5.com/manage/s/article/K000160367
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