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Nginx PlusWeb server / proxy · F5

CVE-2026-28755

MEDIUM · 5.4 CVSS v3.1 Published 2026-03-24
Fix available
A fix is available. Upgrade to 1.28.3 / 1.29.7 or later.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

This vulnerability in NGINX's ngx_stream_ssl_module allows TLS handshakes to succeed even when OCSP validation identifies the client certificate as revoked. When both ssl_verify_client and ssl_ocsp directives are enabled, the OCSP check result is not properly enforced, permitting revoked certificates to authenticate.

MitigationApply vendor-supplied NGINX patches when available. As a temporary workaround, ensure additional certificate validation (such as CRL checking via ssl_crl directive) is in place at the application layer or consider disabling ssl_ocsp until the patch is applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Nginx PlusWeb server / proxy
Affected:= r33= r34= r35= r36
Nginx Open SourceWeb server / proxy
Affected:>= 0.5.13, <= 0.9.7>= 1.27.2, < 1.28.3>= 1.29.0, < 1.29.7

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify NGINX version
    Run 'nginx -v' or 'nginx -V' to obtain the installed version number
    Affected if The version falls within affected ranges: F5 Nginx Plus r33, r34, r35, r36; F5 Nginx Open Source 0.5.13-0.9.7, 1.27.2 to <1.28.3, or 1.29.0 to <1.29.7
  2. Locate NGINX configuration files
    Find all NGINX configuration files, typically in /etc/nginx/nginx.conf and included stream configuration files. Look for 'stream' blocks and their included files.
    Affected if A stream block exists with SSL configuration
  3. Check if client certificate verification is enabled
    In stream block configuration, search for 'ssl_verify_client' directive and verify its value is set to 'on' or 'optional'
    Affected if ssl_verify_client is set to 'on' or 'optional'
  4. Check if OCSP validation is enabled
    In stream block configuration, search for 'ssl_ocsp' directive and verify it is present and enabled
    Affected if ssl_ocsp directive is present in the configuration

A system is affected if it runs a vulnerable NGINX version AND has both ssl_verify_client (on/optional) and ssl_ocsp directives enabled in a stream block configuration.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.28.3 / 1.29.7 or later
Fixed in 1.28.31.29.7
Interim mitigation

Apply vendor-supplied NGINX patches when available. As a temporary workaround, ensure additional certificate validation (such as CRL checking via ssl_crl directive) is in place at the application layer or consider disabling ssl_ocsp until the patch is applied.

Recommended fix High confidence

Nginx Open Source: 1.28.3 or later (for 1.27.x branch), 1.29.7 or later (for 1.29.x branch); Nginx Plus: r37 or later

  1. 1. Identify the currently installed Nginx version using 'nginx -v' or 'nginx -V'
  2. 2. For Nginx Open Source: If running version 1.27.x, upgrade to at least version 1.28.3; if running version 1.29.x, upgrade to at least version 1.29.7
  3. 3. For Nginx Plus: If running r33, r34, r35, or r36, upgrade to r37 or later
  4. 4. After upgrade, verify the version matches the expected fixed release
  5. 5. Test TLS client certificate verification with OCSP validation to confirm revoked certificates are now properly rejected

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Nginx Plus Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-28755 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data