What is CVE-2026-28755?

CVE-2026-28755 is a medium-severity vulnerability in F5 nginx Open Source, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-03-24.

How severe is CVE-2026-28755?

Medium severity. CVSS v3 base score is 5.4 out of 10.

Is CVE-2026-28755 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Auth bypass in F5 nginx Open Source

CVE-2026-28755

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_stream_ssl_module module due to the improper handling of revoked certificates when configured with the ssl_verify_client on and ssl_ocsp on directives, allowing the TLS handshake to succeed even after an OCSP check identifies the certificate as revoked. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Vulnerability class: Broken Access Control

EPSS: 0.001 (3.1th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N.

Affected products

F5 Nginx Open Source — versions 1.29.0, 1.27.2
F5 Nginx_open_source
F5 Nginx Plus — versions R36, R35, R34
F5 Nginx_plus — versions r33, r34, r35

Weakness classification (CWE)

CWE-863 — Incorrect Authorization

Public proof-of-concept exploits

ChPratik/NGINX_2026_CVE_Bundle_CTI_Report

References

f5sirt@f5.com (vendor-advisory, Mitigation, Vendor Advisory)

Frequently asked questions

What is CVE-2026-28755?: CVE-2026-28755 is a medium-severity vulnerability in F5 nginx Open Source, classified under Incorrect Authorization. CVSS score: 5.4/10. Published 2026-03-24.
How severe is CVE-2026-28755?: Medium severity. CVSS v3 base score is 5.4 out of 10.
Is CVE-2026-28755 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.