CVE-2026-28753

6.3 mediumEPSS 0.3%

Medium (6.3) in f5. EPSS 0.3% chance of exploitation in the next 30 days.

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.

Severity

CVSS 4.0

6.3 medium

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

CVSS 3.1

3.7 low

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

EPSS: 0.3% chance of exploitation in the next 30 days; higher than 19% of CVEs (scores of 2026-10-31)
CWE: CWE-93
Published: 2026-03-24
Modified: 2026-06-17
Record from: the NVD, synced 2026-10-19

Affected

f5:nginx_open_source
f5:nginx_plus

References

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

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