CVE-2026-27651
NGINX ngx_mail_auth_http_module vulnerability
Description
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.
INFO
Published Date :
March 24, 2026, 3:16 p.m.
Last Modified :
March 30, 2026, 2:02 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | 9dacffd4-cb11-413f-8451-fbbfd4ddc0ab | ||||
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | HIGH | 9dacffd4-cb11-413f-8451-fbbfd4ddc0ab | ||||
| CVSS 4.0 | HIGH | [email protected] |
Solution
- Disable the ngx_mail_auth_http_module if not required.
- Configure authentication server to not return Auth-Wait header.
- Update NGINX to a non-vulnerable version.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27651.
| URL | Resource |
|---|---|
| https://my.f5.com/manage/s/article/K000160383 | Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27651 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27651
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27651 vulnerability anywhere in the article.
-
Daily CyberSecurity
F5 Out-of-Band Security Alert: Multiple Vulnerabilities Unveiled in NGINX Plus and Open Source
In a significant out-of-band security notification released on March 24, 2026, F5 has disclosed several critical and high-severity vulnerabilities affecting both NGINX Plus and NGINX Open Source. The ... Read more
The following table lists the changes that have been made to the
CVE-2026-27651 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Mar. 30, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:f5:nginx_plus:r32:-:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r32:p1:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r32:p2:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r32:p3:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r35:-:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r36:-:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r36:p1:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:*:*:*:*:*:*:*:* versions from (including) r33 up to (excluding) r35 *cpe:2.3:a:f5:nginx_plus:r35:p1:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_plus:r36:p2:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:* versions from (including) 1.29.0 up to (excluding) 1.29.7 *cpe:2.3:a:f5:nginx_plus:r32:p4:*:*:*:*:*:* *cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:* versions from (including) 1.0.0 up to (excluding) 1.28.3 *cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:* versions from (including) 0.5.15 up to (including) 0.9.7 Added Reference Type F5 Networks: https://my.f5.com/manage/s/article/K000160383 Types: Vendor Advisory -
New CVE Received by [email protected]
Mar. 24, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V4.0 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 Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-476 Added Reference https://my.f5.com/manage/s/article/K000160383