CVE-2026-42530Network attack vector

Remote code execution via reopened QPACK stream

Published Jun 17, 2026 · Updated Jun 17, 2026

Use-after-free in ngx_http_v3_module in F5 NGINX Open Source 1.31.0 through 1.31.1 allows remote attackers to restart workers. The module accepts a reopened QPACK encoder stream from a crafted HTTP/3 session and then accesses freed worker-process memory. HTTP/3 QUIC must be enabled; code execution additionally requires ASLR to be disabled or bypassed.

CVSS severity9.2
Critical
EPSS probability3.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in ngx_http_v3_module in F5 NGINX Open Source 1.31.0 through 1.31.1 allows remote attackers to restart workers. The module accepts a reopened QPACK encoder stream from a crafted HTTP/3 session and then accesses freed worker-process memory. HTTP/3 QUIC must be enabled; code execution additionally requires ASLR to be disabled or bypassed.

The record

CVE
CVE-2026-42530
Published
Jun 17, 2026
Updated
Jun 17, 2026
Vendor
F5 Networks
Product
NGINX Open Source
Classifications
CWE-416, T1190, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 17, 2026CVE publishedPublication date reported by the CVE source.
  2. Jun 17, 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=1.31.0 <1.31.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

F5 Networks · NGINX Open Sourceversion=1.31.0 <1.31.2

Published CVSS scores

8.1F5 NetworksCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.2F5 NetworksCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/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-416Use After Free
T1190Exploit Public-Facing Application
T1499.004Application or System Exploitation

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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