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 which have reached End of Technical Support (EoTS) are not evaluated.

Published · last modified .

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.

EPSS exploit prediction

EPSS: 0.003 (25.6th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 26th percentile — 25.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42926: held from 0.003 to 0.003.

EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: -0.000

Affected products

Weakness classification (CWE)

Public proof-of-concept exploits

References

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.