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NGINX Open Source CVE-2026-42926

| EUVDEUVD-2026-30006 MEDIUM
Encoding Error (CWE-172)
2026-05-13 f5 GHSA-v43f-895r-chhh
6.3
CVSS 4.0 · Vendor: f5
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Severity by source

Vendor (f5) PRIMARY
6.3 MEDIUM
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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
SUSE
5.8 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

Primary rating from Vendor (f5).

CVSS VectorVendor: f5

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/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
Low
Privileges Required
None
User Interaction
None
Scope
X

Lifecycle Timeline

3
CVSS changed
May 13, 2026 - 16:22 NVD
5.8 (MEDIUM) 6.3 (MEDIUM)
Analysis Generated
May 13, 2026 - 16:01 vuln.today
CVE Published
May 13, 2026 - 14:12 nvd
MEDIUM 5.8

DescriptionCVE.org

When NGINX Open Source is configured to proxy HTTP/2 traffic by setting proxy_http_version to 2, and also uses proxy_set_body, an attacker may be able to inject frame headers and payload bytes to the upstream peer.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

AnalysisAI

NGINX Open Source configured to proxy HTTP/2 traffic with proxy_http_version set to 2 combined with proxy_set_body allows remote unauthenticated attackers to inject frame headers and payload bytes to upstream peers, enabling potential header injection or request manipulation attacks. The vulnerability affects default configurations without requiring authentication or user interaction, with CVSS 5.8 indicating moderate integrity impact across networked systems. No public exploit code or active exploitation has been confirmed at this time.

Technical ContextAI

NGINX Open Source implements HTTP/2 proxying through the proxy_http_version directive. When set to version 2, NGINX handles HTTP/2 frame serialization for upstream connections. The vulnerability resides in improper validation of frame boundaries when proxy_set_body is simultaneously configured to modify request bodies. HTTP/2 defines a strict binary framing protocol where each frame type (HEADERS, DATA, etc.) has specific payload structures. CWE-172 (Encoding Error) indicates the root cause involves incorrect handling of encoded data boundaries, allowing attacker-controlled input from proxy_set_body to bypass frame boundary checks and inject arbitrary octets into the serialized HTTP/2 stream sent upstream.

RemediationAI

Apply the vendor-released patch from F5 via advisory K000161131 at https://my.f5.com/manage/s/article/K000161131. Exact patched version numbers are not provided in available data; consult the advisory for your NGINX Open Source branch and release channel. As an interim mitigation, disable HTTP/2 proxying by removing or changing proxy_http_version 2 to 1.1 or 1.0 - this eliminates the vulnerability surface but may reduce upstream connection performance if HTTP/2 multiplexing benefits are required. Alternatively, remove proxy_set_body directives if body modification is not essential to your proxy logic. If both HTTP/2 proxying and body modification are required operationally, prioritize patching immediately as no configuration-only workaround addresses the frame injection flaw. Organizations using NGINX Plus should verify whether equivalent patches are available through F5 support channels.

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-2026-42530 CRITICAL POC
9.2 Jun 17

Use-after-free in NGINX Open Source's ngx_http_v3_module allows remote unauthenticated attackers to crash worker process

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-2026-27654 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-2026-60005 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-2026-27651 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-2026-42946 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-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-

Vendor StatusVendor

SUSE

Severity: Medium
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed
SUSE Linux Enterprise Module for Server Applications 15 SP7 Fixed
SUSE Linux Enterprise Server 15 SP7 Fixed
SUSE Linux Enterprise Server 16.1 Fixed

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CVE-2026-42926 vulnerability details – vuln.today

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