Skip to main content

Nginx Open Source CVE-2026-27651

| EUVDEUVD-2026-14880 HIGH
NULL Pointer Dereference (CWE-476)
2026-03-24 f5
8.7
CVSS 4.0 · Vendor: f5
Share

Severity by source

Vendor (f5) PRIMARY
8.7 HIGH
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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
SUSE
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat
7.5 HIGH
qualitative

Primary rating from Vendor (f5).

CVSS VectorVendor: f5

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

4
Patch released
Apr 10, 2026 - 08:30 nvd
Patch available
EUVD ID Assigned
Mar 24, 2026 - 14:45 euvd
EUVD-2026-14880
Analysis Generated
Mar 24, 2026 - 14:45 vuln.today
CVE Published
Mar 24, 2026 - 14:13 nvd
HIGH 8.7

DescriptionCVE.org

When the ngx_mail_auth_http_module module is enabled on NGINX Plus or NGINX Open Source, undisclosed requests can cause worker processes to terminate. This issue may occur when (1) CRAM-MD5 or APOP authentication is enabled, and (2) the authentication server permits retry by returning the Auth-Wait response header. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

AnalysisAI

NGINX worker process crashes via null pointer dereference in the mail authentication module when CRAM-MD5 or APOP authentication is configured with retry-enabled backend servers. This denial of service vulnerability affects NGINX Plus and NGINX Open Source with no patch currently available, allowing unauthenticated remote attackers to terminate worker processes and degrade service availability.

Technical ContextAI

This vulnerability affects the ngx_mail_auth_http_module in NGINX, which provides HTTP-based authentication for mail proxy functionality. The affected products are NGINX Open Source (cpe:2.3:a:f5:nginx_open_source) and NGINX Plus (cpe:2.3:a:f5:nginx_plus). The root cause is CWE-476 (NULL Pointer Dereference), which occurs when specially crafted requests are processed during CRAM-MD5 or APOP authentication flows when the authentication backend returns an Auth-Wait header instructing the proxy to retry authentication. This architectural flaw in pointer handling during the authentication retry mechanism allows the worker process to access invalid memory locations, leading to process termination.

RemediationAI

Consult the F5 security advisory at https://my.f5.com/manage/s/article/K000160383 for specific patch versions and upgrade instructions for both NGINX Open Source and NGINX Plus. Organizations should prioritize upgrading to patched versions provided by F5 that address the null pointer dereference in the mail authentication module. As an immediate mitigation for environments that cannot patch immediately, administrators should consider disabling CRAM-MD5 and APOP authentication methods in favor of alternative authentication mechanisms, or disable the Auth-Wait retry functionality on the authentication backend if business requirements permit. For deployments where the mail proxy functionality is not required, disabling the ngx_mail_auth_http_module entirely eliminates exposure. Network-level controls such as restricting access to mail proxy ports to trusted IP ranges can reduce attack surface but do not eliminate the vulnerability for legitimate users.

CVE-2026-42945 CRITICAL POC
9.2 May 13

Heap buffer overflow in NGINX Plus and NGINX Open Source ngx_http_rewrite_module allows remote attackers to crash worker

CVE-2026-42530 CRITICAL POC
9.2 Jun 17

Use-after-free in NGINX Open Source's ngx_http_v3_module allows remote unauthenticated attackers to crash worker process

CVE-2026-42055 CRITICAL POC
9.2 Jun 17

Heap-based buffer overflow in NGINX Plus and NGINX Open Source affects deployments that proxy HTTP/2 or gRPC traffic ups

CVE-2026-9256 CRITICAL POC
9.2 May 22

Heap buffer overflow in NGINX Plus and NGINX Open Source ngx_http_rewrite_module can be triggered by unauthenticated rem

CVE-2026-42533 CRITICAL
9.2 Jul 15

Heap buffer overflow in NGINX Plus and NGINX Open Source lets unauthenticated remote attackers crash worker processes (D

CVE-2026-27654 HIGH
8.8 Mar 24

Buffer overflow in NGINX's DAV module allows remote attackers to crash worker processes or manipulate file names outside

CVE-2026-60005 HIGH
8.8 Jul 15

Limited memory disclosure and worker-process restart in NGINX Plus and NGINX Open Source arise when the optional ngx_htt

CVE-2026-27784 HIGH
8.5 Mar 24

Integer overflow in NGINX 32-bit builds with the ngx_http_mp4_module allows local attackers to corrupt or overwrite work

CVE-2026-32647 HIGH
8.5 Mar 24

NGINX Open Source and NGINX Plus contain a buffer over-read or over-write vulnerability in the ngx_http_mp4_module that

CVE-2026-42946 HIGH
8.3 May 13

Memory disclosure and denial-of-service in NGINX's SCGI and uWSGI proxy modules allow attackers with man-in-the-middle p

CVE-2026-56434 HIGH
8.3 Jul 15

Heap buffer over-read in the ngx_http_ssi_module of NGINX Open Source and NGINX Plus lets an unauthenticated man-in-the-

CVE-2024-24990 HIGH
7.5 Feb 14

When NGINX Plus or NGINX OSS are configured to use the HTTP/3 QUIC module, undisclosed requests can cause NGINX worker p

Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Liberty Linux 8 Fixed
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Server Applications 15 SP7 Fixed
SUSE Linux Enterprise Server 15 SP7 Fixed

Share

CVE-2026-27651 vulnerability details – vuln.today

This site uses cookies essential for authentication and security. No tracking or analytics cookies are used. Privacy Policy