SB2026032585 - Multiple vulnerabilities in NGINX Open Source and NGINX Plus

Description

This security bulletin contains information about 6 secuirty vulnerabilities.

1) CRLF injection (CVE-ID: CVE-2026-28753)

The vulnerability allows a remote attacker to inject arbitrary data in server response.

The vulnerability exists due to insufficient validation of attacker-supplied data in the ngx_mail_smtp_module module when handling DNS responses. A remote attacker can inject arbitrary headers into SMTP upstream requests and manipulate data.

2) Integer overflow (CVE-ID: CVE-2026-27784)

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to integer overflow in the ngx_http_mp4_module module. A remote attacker can supply specially crafted MP4 data to the server, trigger an integer overflow and execute arbitrary code on the target system.

Note, the vulnerability affects only 32-bit NGINX Open Source deployments. 

3) Heap-based buffer overflow (CVE-ID: CVE-2026-27654)

The vulnerability allows a remote attacker to perform a denial of service attack.

The vulnerability exists due to a boundary error in the ngx_http_dav_module module. A remote attacker can send specially crafted request to the server, trigger a heap-based buffer overflow and perform a denial of service attack or modify source or destination file names outside the document root. 

4) Out-of-bounds write (CVE-ID: CVE-2026-32647)

The vulnerability allows a remote attacker to compromise vulnerable system.

The vulnerability exists due to a boundary error in the ngx_http_mp4_module module. A remote attacker can supply a specially crafted MP4 file to the server, trigger an out-of-bounds write and execute arbitrary code on the target system.

5) NULL pointer dereference (CVE-ID: CVE-2026-27651)

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to a NULL pointer dereference error within the ngx_mail_auth_http_module module. A remote attacker can send specially crafted request to the server and perform a denial of service (DoS) attack.

Successful exploitation of the vulnerability requires that the CRAM-MD5 or APOP authentication is enabled, and the authentication server permits retry by returning the Auth-Wait response header.

6) Incorrect authorization (CVE-ID: CVE-2026-28755)

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to improper handling of revoked certificates in the ngx_stream_ssl_module module when configured with the ssl_verify_client on and ssl_ocsp on directives. A remote attacker can bypass authorization checks and access application data with a revoked certificate. 

Remediation

Install update from vendor's website.

References

• https://my.f5.com/manage/s/article/K000160367
• https://my.f5.com/manage/s/article/K000160364
• https://my.f5.com/manage/s/article/K000160382
• https://my.f5.com/manage/s/article/K000160366
• https://my.f5.com/manage/s/article/K000160383
• https://my.f5.com/manage/s/article/K000160368