CVE-2026-28755: NGINX ngx_stream_ssl_module vulnerability

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-03-24 · updated 2026-06-17
Weakness: CWE-863

Description

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.

Affected products

F5 NGINX Open Source: from 0.5.13 through 0.9.7; from 1.27.2 before 1.28.3; from 1.29.0 before 1.29.7 — fixed in 1.28.3, 1.29.7
F5 NGINX Plus: r33, r33-p1, r33-p2, r33-p3, r34, r34-p1 (+5)

How to fix

Upgrade to a fixed version: F5 NGINX Open Source 1.28.3, 1.29.7. Check the vendor advisory for mitigations.

References

https://my.f5.com/manage/s/article/K000160368

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