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NGINX Open Source CVE-2026-42530

CRITICAL
Use After Free (CWE-416)
2026-06-17 f5
9.2
CVSS 4.0 · Vendor: f5
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Severity by source

Vendor (f5) PRIMARY
9.2 HIGH
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
vuln.today AI
8.1 HIGH

Network-reachable HTTP/3 listener with no auth or user interaction (AV:N/PR:N/UI:N); AC:H reflects vendor-stated conditions beyond attacker control and ASLR dependency for RCE; full C/I/A on worker compromise.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE
8.1 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Red Hat
8.1 HIGH
qualitative

Primary rating from Vendor (f5).

CVSS VectorVendor: f5

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
Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

7
Analysis Updated
Jun 18, 2026 - 04:59 vuln.today
v3 (cvss_changed)
Analysis Updated
Jun 18, 2026 - 04:59 vuln.today
v2 (cvss_changed)
Re-analysis Queued
Jun 18, 2026 - 04:52 vuln.today
cvss_changed
Severity Changed
Jun 18, 2026 - 04:52 NVD
HIGH CRITICAL
CVSS changed
Jun 18, 2026 - 04:52 NVD
8.1 (HIGH) 9.2 (CRITICAL)
Analysis Generated
Jun 17, 2026 - 15:30 vuln.today
CVE Published
Jun 17, 2026 - 14:04 cve.org
HIGH 8.1

DescriptionCVE.org

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.

AnalysisAI

Use-after-free in NGINX Open Source's ngx_http_v3_module allows remote unauthenticated attackers to crash worker processes and potentially execute arbitrary code on hosts where HTTP/3 QUIC is enabled. Exploitation requires a specially crafted HTTP/3 session that reopens a QPACK encoder stream, with code execution contingent on ASLR being disabled or bypassed; no public exploit identified at time of analysis, though SSVC technical impact is rated total.

Technical ContextAI

The flaw resides in the ngx_http_v3_module, which implements HTTP/3 over QUIC and uses QPACK (RFC 9204) for header compression. QPACK relies on a dedicated unidirectional encoder stream from client to server to maintain a dynamic table of header field representations; per spec there must only ever be one encoder stream per connection. By inducing the server to reopen this stream mid-session, the attacker triggers CWE-416 (Use-After-Free) inside the NGINX worker, where a freed QPACK decoder/stream context is dereferenced. The affected CPE is cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:*, covering supported NGINX Open Source branches that ship the HTTP/3 module; F5 explicitly excludes End-of-Technical-Support versions from evaluation.

RemediationAI

Patch available per vendor advisory: upgrade NGINX Open Source to the fixed branch released by F5 as detailed in https://my.f5.com/manage/s/article/K000161616 (cite the exact fix version from that advisory for change-management). If immediate patching is not possible, the most effective workaround is to disable HTTP/3 by removing the 'quic' parameter from any 'listen ... quic' directives and reloading NGINX, which fully removes the vulnerable code path at the cost of losing HTTP/3 client support and forcing fallback to HTTP/2 or HTTP/1.1. As a hardening measure, ensure ASLR is enabled kernel-wide (kernel.randomize_va_space=2 on Linux) and that NGINX binaries and loaded modules are PIE-compiled, which neutralizes the code-execution path described by the vendor and reduces the bug to a worker restart denial-of-service; restricting UDP/443 ingress at upstream load balancers or firewalls to trusted networks is an additional compensating control where HTTP/3 must remain enabled.

CVE-2026-42945 CRITICAL POC
9.2 May 13

Heap buffer overflow in NGINX Plus and NGINX Open Source ngx_http_rewrite_module allows remote attackers to crash worker

CVE-2026-42055 CRITICAL POC
9.2 Jun 17

Heap-based buffer overflow in NGINX Plus and NGINX Open Source affects deployments that proxy HTTP/2 or gRPC traffic ups

CVE-2026-9256 CRITICAL POC
9.2 May 22

Heap buffer overflow in NGINX Plus and NGINX Open Source ngx_http_rewrite_module can be triggered by unauthenticated rem

CVE-2026-42533 CRITICAL
9.2 Jul 15

Heap buffer overflow in NGINX Plus and NGINX Open Source lets unauthenticated remote attackers crash worker processes (D

CVE-2026-60005 HIGH
8.8 Jul 15

Limited memory disclosure and worker-process restart in NGINX Plus and NGINX Open Source arise when the optional ngx_htt

CVE-2026-27654 HIGH
8.8 Mar 24

Buffer overflow in NGINX's DAV module allows remote attackers to crash worker processes or manipulate file names outside

CVE-2026-27651 HIGH
8.7 Mar 24

NGINX worker process crashes via null pointer dereference in the mail authentication module when CRAM-MD5 or APOP authen

CVE-2026-27784 HIGH
8.5 Mar 24

Integer overflow in NGINX 32-bit builds with the ngx_http_mp4_module allows local attackers to corrupt or overwrite work

CVE-2026-32647 HIGH
8.5 Mar 24

NGINX Open Source and NGINX Plus contain a buffer over-read or over-write vulnerability in the ngx_http_mp4_module that

CVE-2026-56434 HIGH
8.3 Jul 15

Heap buffer over-read in the ngx_http_ssi_module of NGINX Open Source and NGINX Plus lets an unauthenticated man-in-the-

CVE-2026-42946 HIGH
8.3 May 13

Memory disclosure and denial-of-service in NGINX's SCGI and uWSGI proxy modules allow attackers with man-in-the-middle p

CVE-2024-24990 HIGH
7.5 Feb 14

When NGINX Plus or NGINX OSS are configured to use the HTTP/3 QUIC module, undisclosed requests can cause NGINX worker p

Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Not-Affected
SUSE Linux Enterprise Module for Server Applications 15 SP7 Not-Affected
SUSE Linux Enterprise Server 15 SP7 Not-Affected
SUSE Linux Enterprise Server 16.0 Not-Affected

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CVE-2026-42530 vulnerability details – vuln.today

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