What is CVE-2026-42926?

CVE-2026-42926 is a medium-severity vulnerability in F5 Nginx Open Source, 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.

Vulnerability in F5 Nginx Open Source

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: 0.000 (6.7th 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 Open Source — versions 1.31.0, 1.29.4

Weakness classification (CWE)

CWE-172

References

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

Frequently asked questions

What is CVE-2026-42926?: CVE-2026-42926 is a medium-severity vulnerability in F5 Nginx Open Source, 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.