CVE-2026-40460Network attack vector

Authorization bypass via premature QUIC address assignment

Published May 13, 2026 · Updated May 13, 2026

Authentication bypass in affected F5 NGINX Open Source and NGINX Plus releases allows remote attackers to spoof source IP addresses. During QUIC connection migration, ngx_quic_handle_migration assigns a newly presented network address to new streams before path validation completes. Exposure requires HTTP/3 QUIC configuration; the false source address can bypass IP-based authorization or rate limits and cause limited service interruption.

CVSS severity6.9
Medium
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authentication bypass in affected F5 NGINX Open Source and NGINX Plus releases allows remote attackers to spoof source IP addresses. During QUIC connection migration, ngx_quic_handle_migration assigns a newly presented network address to new streams before path validation completes. Exposure requires HTTP/3 QUIC configuration; the false source address can bypass IP-based authorization or rate limits and cause limited service interruption.

The record

CVE
CVE-2026-40460
Published
May 13, 2026
Updated
May 13, 2026
Vendor
F5 Networks
Product
NGINX Open Source
Classifications
CWE-290, CAPEC-21, CAPEC-22, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=1.26.0 <1.30.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · NGINX Open Sourceversion=1.26.0 <1.30.1
F5 Networks · NGINX Plusversion=R32 <R32 P6; version=R36 <R36 P4

Published CVSS scores

6.5F5 NetworksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
6.9F5 NetworksCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
CAPEC-21Exploitation of Trusted Identifiers
CAPEC-22Exploiting Trust in Client
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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