CVE-2026-28753 | F5 NGINX Open Source/NGINX Plus ngx_mail_smtp_module crlf injection (K000160367)

VDB-352785 · CVE-2026-28753 · K000160367 F5 NGINX OPEN SOURCE/NGINX PLUS NGX_MAIL_SMTP_MODULE CRLF INJECTION HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 3.7 $0-$5k 0.58+ Summaryinfo A vulnerability classified as problematic has been found in F5 NGINX Open Source and NGINX Plus. This issue affects the function ngx_mail_smtp_module. Performing a manipulation results in crlf injection. This vulnerability is known as CVE-2026-28753. Remote exploitation of the attack is possible. No exploit is available. It is recommended to upgrade the affected component. Detailsinfo A vulnerability, which was classified as problematic, was found in F5 NGINX Open Source and NGINX Plus (version now known). This affects the function ngx_mail_smtp_module. The manipulation with an unknown input leads to a crlf injection vulnerability. CWE is classifying the issue as CWE-93. The product uses CRLF (carriage return line feeds) as a special element, e.g. to separate lines or records, but it does not neutralize or incorrectly neutralizes CRLF sequences from inputs. This is going to have an impact on integrity. The summary by CVE is: 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. The advisory is shared at my.f5.com. This vulnerability is uniquely identified as CVE-2026-28753 since 03/18/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 03/24/2026). Upgrading eliminates this vulnerability. Productinfo Type Web Server Vendor F5 Name NGINX Open Source NGINX Plus License commercial Website Vendor: https://f5.com/ CPE 2.3info 🔒 CPE 2.2info 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 3.7 VulDB Meta Temp Score: 3.7 VulDB Base Score: 3.7 VulDB Temp Score: 3.6 VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA Base Score: 3.7 CNA Vector: 🔒 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Crlf injection CWE: CWE-93 / CWE-74 / CWE-707 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Timelineinfo 03/18/2026 CVE reserved 03/24/2026 +6 days Advisory disclosed 03/24/2026 +0 days VulDB entry created 03/24/2026 +0 days VulDB entry last update Sourcesinfo Vendor: f5.com Advisory: K000160367 Status: Confirmed CVE: CVE-2026-28753 (🔒) GCVE (CVE): GCVE-0-2026-28753 GCVE (VulDB): GCVE-100-352785 Entryinfo Created: 03/24/2026 16:08 Changes: 03/24/2026 16:08 (75) Complete: 🔍 Cache ID: 99:BDB:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸