NGINX ngx_mail_proxy_module vulnerability
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.
- Published
- Mar 24, 2026
- Updated
- Jun 17, 2026
- EPSS
- 0.3% · 18th percentile
- CWE
- CWE-93
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Report tools
Action score
25
Monitor
Low priority for now.
- CVSS
- 25 / 40 · 6.3 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.3%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · f5
- 3.7
- NVD has not scored this yet; the score shown is the CNA’s.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Affected systems
| Vendor | Product | CPE |
|---|---|---|
| f5 | nginx plus | cpe:2.3:a:f5:nginx_plus |
| f5 | nginx open source | cpe:2.3:a:f5:nginx_open_source |
Using nginx plus? Add it to your stack and be the first to know about CVEs like this one. (Nginx)
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- f5 nginx open source0.6.27 and later · up to 0.9.7 inclusive
- f5 nginx open source1.29.0 and later · before 1.29.7
- f5 nginx open source1.0.0 and later · before 1.28.3
- f5 nginx plusr32
- f5 nginx plusr33
- f5 nginx plusr34
- f5 nginx plusr35
- f5 nginx plusr36
Versions reported by the vendor
Affected version ranges reported by the assigning authority (f5). Independent of NVD's CPE analysis and usually ahead of it.
F5 NGINX Open Source
- 1.29.0 and later · before 1.29.7affected · semver
- 0.6.27 and later · before 1.28.3affected · semver
F5 NGINX Plus
- R36 and later · before R36 P3affected
- R35 and later · before R35 P2affected
- R34 and lateraffected
- R33 and lateraffected
- R32 and later · before R32 P5affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.22 | nginx | before 1.28.3-r0 | 1.28.3-r0 |
| Debian:12 | nginx | before 1.22.1-9+deb12u5 | 1.22.1-9+deb12u5 |
| Debian:13 | nginx | before 1.26.3-3+deb13u3 | 1.26.3-3+deb13u3 |
| Debian:14 | nginx | before 1.28.3-1 | 1.28.3-1 |
| openSUSE:Tumbleweed | nginx | before 1.29.7-1.1 | 1.29.7-1.1 |
| Red Hat:hummingbird:1 | nginx | before 0:1.30.0-1.hum1 | 0:1.30.0-1.hum1 |
| Red Hat:hummingbird:1 | nginx-all-modules | before 0:1.30.0-1.hum1 | 0:1.30.0-1.hum1 |
Same product
f5: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-27654NGINX ngx_http_dav_module vulnerability35Monitor
- CVE-2026-32647NGINX ngx_http_mp4_module vulnerability34Monitor
- CVE-2024-39792NGINX Plus MQTT vulnerability34Monitor
- CVE-2026-90439NGINX ngx_http_v3_module vulnerability27Monitor
- CVE-2025-53859NGINX ngx_mail_smtp_module vulnerability25Monitor
- CVE-2026-28755NGINX ngx_stream_ssl_module vulnerability21Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| F5 NGINX Open Source | 1.28.3 | Vendor (CNA) |
| F5 NGINX Open Source | 1.29.7 | Vendor (CNA) |
| alpine:nginx | 1.28.3-r0 · Alpine:v3.22 | Package registry (OSV) |
| debian:nginx | 1.22.1-9+deb12u5 · Debian:12 | Package registry (OSV) |
| opensuse:nginx | 1.29.7-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
| red hat:nginx | 0:1.30.0-1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:nginx-all-modules | 0:1.30.0-1.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- Bird Liu (Lanzhou University)reporter
- Asim Viladi Oglu Manizadareporter
- Colin Warrenreporter
- Xiao Liu (Yunnan University)reporter
- Yuan Tan (UC Riverside)reporter
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- Special conditions such as timing or configuration are required.
If successful
- Confidentiality
- Integrity
- Availability
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- None
- User interaction
- None
- Scope
- X
Weakness class (CWE)
CWE-93 · Improper Neutralization of CRLF Sequences ('CRLF Injection')CVSS vector
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
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Attack patterns (CAPEC)
ATT&CK techniques
—
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for all 385,000+ vulnerabilities; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpChange log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Vendor advisories and official records. Exploit/PoC links are deliberately left out.