CVE-2026-27651
High
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.
SeverityHigh
CVSS7.5
Exploit probability—
Product
F5 Nginx Open Source
PublishedMar 24, 2026
First seenMar 24, 2026
Weakness typeCWE-476NULL pointer dereference
How to fix
Update
- f5 nginx_open_source1.28.3, 1.29.7 or later
- f5 nginx_plusr35 or later
Vendor advisories
- my.f5.com/manage/s/article/K000160383
- access.redhat.com/errata/RHSA-2026:13634
- access.redhat.com/errata/RHSA-2026:6906
- access.redhat.com/errata/RHSA-2026:6907
- access.redhat.com/errata/RHSA-2026:15942
- access.redhat.com/errata/RHSA-2026:14836
- access.redhat.com/errata/RHSA-2026:13839
- access.redhat.com/errata/RHSA-2026:15943
- access.redhat.com/errata/RHSA-2026:15945
- access.redhat.com/errata/RHSA-2026:13680
- access.redhat.com/errata/RHSA-2026:15966
- access.redhat.com/errata/RHSA-2026:6923
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| f5 nginx_open_source | 0.5.15 ≤ v ≤ 0.9.7, 1.0.0 ≤ v < 1.28.3, 1.29.0 ≤ v < 1.29.7 | 1.28.3, 1.29.7 |
| f5 nginx_plus | r33 ≤ v < r35, r32, r35, r36 | r35 |
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