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DosApplication · F5

CVE-2026-42946

HIGH · 7.4 CVSS v3.1 Published 2026-05-13
Fix available
A fix is available. Upgrade to after 5.12.1 or later.
See remediation →
83/100
Remediation priority · High
Remotely reachable No privileges 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
A vulnerability exists in the ngx_http_scgi_module and ngx_http_uwsgi_module modules that may result in excessive memory allocation or an over-read of data. When scgi_pass or uwsgi_pass is configured, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to read the memory of the NGINX worker process or restart it.  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

A memory handling vulnerability in NGINX's ngx_http_scgi_module and ngx_http_uwsgi_module allows an unauthenticated attacker with MITM capability over the upstream connection to cause excessive memory allocation or over-read, potentially exposing worker process memory or causing worker restarts when scgi_pass or uwsgi_pass directives are in use.

MitigationEnsure upstream SCGI/uWSGI connections are protected with TLS encryption to prevent MITM attacks, and upgrade NGINX to a version containing the security fix once available.

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
DosApplication
Affected:>= 4.3.0, <= 4.7.0= 4.8.0
Nginx Gateway FabricWeb server / proxy
Affected:>= 1.3.0, <= 1.6.2>= 2.0.0, <= 2.6.0
Nginx Ingress ControllerWeb server / proxy
Affected:>= 3.5.0, <= 3.7.2>= 4.0.0, <= 4.0.1>= 5.0.0, <= 5.4.2
Nginx Instance ManagerWeb server / proxy
Affected:>= 2.16.0, <= 2.22.0
Nginx Open SourceWeb server / proxy
Affected:>= 0.8.42, <= 0.9.7>= 1.0.0, <= 1.30.0
Nginx PlusWeb server / proxy
Affected:>= r32, <= r36
WafApplication
Affected:>= 4.9.0, <= 4.16.0>= 5.1.0, <= 5.8.0>= 5.9.0, <= 5.12.1

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

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

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 product and version
    Run 'nginx -v' to get version info. For F5 products, also check package manager (rpm -q or dpkg -l) for the specific F5 NGINX package name and version.
    Affected if Version falls within affected ranges: NGINX Open Source <=0.9.7 or 1.0.0-1.30.0; NGINX Plus r32-r36; or any F5 product version listed in affected ranges.
  2. Verify scgi_pass or uwsgi_pass directives are in use
    Search NGINX configuration files for 'scgi_pass' or 'uwsgi_pass' directives using: 'grep -r "scgi_pass\|uwsgi_pass" /etc/nginx/' or check your active configuration.
    Affected if Any scgi_pass or uwsgi_pass directive is found in active NGINX configuration, as this enables the vulnerable code paths.
  3. Check if upstream connections are unencrypted
    Examine the configuration around scgi_pass/uwsgi_pass directives. Look for whether the upstream backend specifies a protocol (like 'unix:', '127.0.0.1:', or missing 'https://'). Check if 'proxy_ssl' or equivalent TLS encryption is configured for the SCGI/uWSGI upstream.
    Affected if The scgi_pass or uwsgi_pass points to an unencrypted backend (unix socket, plain TCP, or HTTP without TLS wrapping), making MITM attack possible.
  4. For F5-specific products, verify product version
    F5 DoS: check version in UI or via 'f5-version' command. F5 Nginx Gateway Fabric: 'kubectl get pods -A | grep nginx-gateway'. F5 Nginx Ingress Controller: 'kubectl get pods -A | grep nginx-ingress'. F5 Nginx Instance Manager: check web UI or API. Compare versions against affected ranges for each product.
    Affected if Running any affected F5 product version within the ranges listed in the CVE (e.g., F5 NGINX Ingress Controller 3.5.0-3.7.2, 4.0.0-4.0.1, or 5.0.0-5.4.2).

You are affected if you run any NGINX version within the affected ranges AND have scgi_pass or uwsgi_pass directives pointing to unencrypted upstream connections that could be intercepted by a MITM attacker.

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.

From vendor data
Upgrade available Upgrade to a release after 5.12.1
Interim mitigation

Ensure upstream SCGI/uWSGI connections are protected with TLS encryption to prevent MITM attacks, and upgrade NGINX to a version containing the security fix once available.

Fix this in Dos Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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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-2026-42946 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