Threat Intelligence / CVE / CVE-2026-42530

CVE-2026-42530 — F5 NGINX Open Source

CVSS v3.1 8.1 (HIGH) · CVSS v4.0 9.2 · EPSS 2.3% (higher than 81.8% of all scored CVEs) · Priority 9.3/10 · Published 2026-06-17

As of 2026-06-18, CVE-2026-42530 is a HIGH-severity vulnerability in F5 NGINX Open Source, CVSS v3.1 8.1, EPSS 2.3% (81.8th percentile). Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2026-42530, most recently “F5 Out-of-Band Patches for Critical NGINX HTTP/3 Use-After-Free and Proxy/gRPC Heap Overflow (CVE-2026-42530, CVE-2026-42055) plus NGINX Gateway Fabric Config Injection (CVE-2026-11311, CVE-2026-50107)”.

Last updated: 2026-06-18

What is CVE-2026-42530?

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.

The record classifies CVE-2026-42530 under weakness class CWE-416. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 87 days ago.

Severity and exploitation probability

CVSS v3.1 base score
8.1 — HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS v4.0 base score
9.2
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
EPSS (FIRST)
2.3% probability of exploitation in the next 30 days, higher than 81.8% of all scored CVEs
CISA KEV
Not listed in the CISA Known Exploited Vulnerabilities catalog
Threadlinqs priority
9.3/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
Published
2026-06-17, last modified 2026-06-18

Is CVE-2026-42530 being exploited?

Weaponised exploit code for CVE-2026-42530 is publicly available. 3 public proof-of-concept repositories are tracked for this identifier.

Affected products and versions

How to fix CVE-2026-42530

No vendor patch reference has been recorded for CVE-2026-42530 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

Threat activity tracking CVE-2026-42530

1 tracked threat in the Threadlinqs corpus references CVE-2026-42530, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Enriched from CVE.org, NVD, FIRST EPSS, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.

Vendor advisory and patch

Full detection coverage & IOCs for threats exploiting CVE-2026-42530 are available via the Threadlinqs MCP server (Purple tier). View plans →

← all vulnerabilities · Markdown version · Threadlinqs Intelligence