Cyber Resilience

CVE-2026-40460

Auth Bypass in F5 Nginx Ingress Controller 3.5.0 – 3.7.2

Auth Bypass
Published
13 May 2026
Modified
29 June 2026
Patch / advisory
View advisory
CVSS Score v4 6.9
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0037 29th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-40460 is a medium-severity Authentication Bypass by Spoofing (CWE-290) vulnerability in F5 Nginx Ingress Controller. Its CVSS base score is 6.9 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 29th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to AC-3 (Access Enforcement) and SC-7 (Boundary Protection) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

A07:2025 Authentication Failures

EU & UK References

Vulnerability Data

When NGINX Plus or NGINX Open Source are configured to use the HTTP/3 QUIC module, an attacker may be able to spoof their source IP address allowing for bypass of authorization or bypass of rate limiting. Note: Software versions which…

more

have reached End of Technical Support (EoTS) are not evaluated.

CWE(s)
CWE-290

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
Why these techniques?

CVE enables source IP spoofing to bypass auth/rate limits on public NGINX HTTP/3 endpoint, directly facilitating T1190 exploitation of public-facing application.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-40701Same product: F5 Dos
CVE-2026-48142Same product: F5 Dos
CVE-2026-42934Same product: F5 Dos
CVE-2026-42945Same product: F5 Dos
CVE-2026-42055Same product: F5 Dos
CVE-2026-42530Same product: F5 Nginx Gateway Fabric
CVE-2026-42926Same product: F5 Nginx Gateway Fabric
CVE-2026-42946Same product: F5 Dos
CVE-2026-9256Same product: F5 Nginx Open Source
CVE-2026-1642Same product: F5 Nginx Gateway Fabric

Affected Assets

f5
dos
4.8.0 · 4.3.0 — 4.7.0
f5
nginx gateway fabric
1.3.0 — 1.6.2 · 2.0.0 — 2.6.0
f5
nginx ingress controller
3.5.0 — 3.7.2 · 4.0.0 — 4.0.1 · 5.0.0 — 5.4.2
f5
nginx instance manager
2.16.0 — 2.22.0
f5
nginx open source
1.25.0 — 1.30.0
f5
nginx plus
r32 — r36
f5
waf
4.9.0 — 4.16.0 · 5.1.0 — 5.8.0 · 5.9.0 — 5.12.1

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • AC-3 Access Enforcement
  • SC-7 Boundary Protection
  • AC-4 Information Flow Enforcement
Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)
  • 3 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)
  • V6.4.3
  • V10.4.16
  • V10.5.1
  • V11.4.3

Mitigating Controls (NIST 800-53 r5) AI

AC-3 Access Enforcement good match
prevent

Directly enforces authorization decisions; the CVE allows spoofed source IPs to bypass those decisions when they rely on client IP.

SC-7 Boundary Protection good match
prevent

Boundary protection (ingress filtering, anti-spoofing) stops forged source addresses from reaching the NGINX QUIC listener.

AC-4 Information Flow Enforcement partial match
prevent

Enforces information flow rules that can be keyed on verified rather than spoofable source attributes, mitigating both auth and rate-limit bypass.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.AA-04 full match
prevents

Protecting, conveying, and verifying identity assertions specifically prevents the spoofing that enables authentication bypass.

PR.AA-03 mostly match
prevents

Requiring authentication of users/services/hardware directly counters spoofing-based bypass when strong methods are used.

PR.AA-02 partial match
prevents

Proofing and binding identities reduces spoofing opportunities during enrollment but does not address runtime authentication implementation flaws.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.5 Secure authentication full match
degrades

Secure authentication control directly mitigates authentication bypass by spoofing.

A.5.17 Authentication information mostly match
degrades

Authentication information management directly addresses credential handling that prevents spoofing.

A.8.29 Security testing in development and acceptance mostly match
detects

Security testing can detect spoofing vulnerabilities but does not prevent them by itself.

A.5.15 Access control partial match
prevents

Access control policy reduces spoofing opportunities but does not prescribe authentication mechanisms.

A.5.16 Identity management partial match
prevents

Identity management supports unique identities but does not guarantee resistance to spoofing.

A.5.18 Access rights partial match
prevents

Access rights assignment limits exposure but does not enforce authentication strength.

References