What is CVE-2026-42926?

CVE-2026-42926 is a medium-severity vulnerability in F5 Nginx_gateway_fabric, classified under CWE-172. CVSS score: 5.8/10. Published 2026-05-13.

How severe is CVE-2026-42926?

Medium severity. CVSS v3 base score is 5.8 out of 10.

Is CVE-2026-42926 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in F5 Nginx_gateway_fabric

CVE-2026-42926

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…

EPSS: 0.003 (26.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.8 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N.

Affected products

F5 Nginx_gateway_fabric
F5 Nginx_ingress_controller
F5 Nginx_instance_manager
F5 Nginx Open Source — versions 1.31.0, 1.29.4
F5 Nginx_open_source

Weakness classification (CWE)

CWE-172

Public proof-of-concept exploits

ikarolaborda/CVE2026-42926

References

f5sirt@f5.com (vendor-advisory, Mitigation, patch, Vendor Advisory)

Frequently asked questions

What is CVE-2026-42926?: CVE-2026-42926 is a medium-severity vulnerability in F5 Nginx_gateway_fabric, classified under CWE-172. CVSS score: 5.8/10. Published 2026-05-13.
How severe is CVE-2026-42926?: Medium severity. CVSS v3 base score is 5.8 out of 10.
Is CVE-2026-42926 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.