Public proof of conceptFix available

CVE-2026-42530

Q: Is CVE-2026-42530 actively exploited?

Active exploitation of CVE-2026-42530 has not been confirmed. Its EPSS score was 1.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-42530?

CVE-2026-42530 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2026-06-17
Fixed in5.5.1
WeaknessCWE-416

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

NGINX Open Source has a vulnerability in the ngx_http_v3_module module. When NGINX Open Source is configured to use the HTTP/3 QUIC module, a remote unauthenticated attacker along with conditions beyond their control can use a specially crafted HTTP/3 session to reopen a QPACK encoder stream. This may cause a Use-after-Free in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

Timeline

dates in UTC

2026-06-1715:16CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-42530?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-42530?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

F5 nginx ingress controller

Branch	Affected	Fixed in	Source
5.x	≥ 5.0.0, < 5.5.1	5.5.1	NVD
3.x	≥ 3.5.0, ≤ 3.7.2	no fix published	NVD
4.0	= 4.0.0	no fix published	NVD
4.0	= 4.0.1	no fix published	NVD

F5 nginx gateway fabric

Branch	Affected	Fixed in	Source
2.x	≥ 2.0.0, < 2.6.4	2.6.4	NVD
1.x	≥ 1.3.0, ≤ 1.6.2	no fix published	NVD

F5 nginx instance manager

Branch	Affected	Fixed in	Source
2.x	≥ 2.17.0, ≤ 2.22.0	no fix published	NVD

1 more product in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update F5 nginx ingress controller to 5.5.1

Advisories and patches

my.f5.comVendor Advisory

Detection

read 2026-10-23 19:25 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 3 repositories, unverifiedHORKimhab/CVE-2026-42530v4ltonn/CVE-2026-425300xBlackash/CVE-2026-42530

Sources

NVDCVE recordread 2026-10-23
CISA-ADPSSVC decisionnone2026-06-17
OpenCVESSVC decisionnone—
CNACVSS 4.09.2read 2026-10-23
CNACVSS 3.18.1read 2026-10-23
CNAweakness (CWE)CWE-416read 2026-10-23
FIRST EPSSEPSS score1.5 %2026-10-23
PoC-in-GitHubproof of concept3read 2026-10-23
OSVaffected packages—

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 4.0 vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/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
Published: 2026-06-17
Last Modified: 2026-07-16
NVD status: Modified

Frequently asked questions

What is CVE-2026-42530?

Is CVE-2026-42530 actively exploited?

Active exploitation of CVE-2026-42530 has not been confirmed. Its EPSS score was 1.5% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-42530?

CVE-2026-42530 has a CVSS v3 base score of 8.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

Running nginx? Hear about its next vulnerability

Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».

Get alerts for this product CISA KEV additions, October 2026 Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
Running this software? Vulnerability monitoring alerts you to new vulnerabilities in your products.

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database