NULL pointer dereference in F5 nginx Open Source
CVE-2026-27651
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.017 (76.5th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 77th percentile — 76.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.009 · newest: 0.017 · change: +0.007
Affected products
- F5 nginx Open Source — versions 1.29.0, 0.5.15
- F5 nginx Open Source
- F5 nginx Plus — versions R36, R35, R34
- F5 nginx Plus — versions r32, r35, r36
Weakness classification (CWE)
References
- my.f5.com/manage/s/article/K000160383 (vendor-advisory, Vendor Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-27651?
- CVE-2026-27651 is a high-severity vulnerability in F5 nginx Open Source, classified under NULL Pointer Dereference. CVSS score: 7.5/10. Published 2026-03-24.
- How severe is CVE-2026-27651?
- High severity. CVSS v3 base score is 7.5 out of 10.