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CVE-2026-42926

MEDIUMCVSS 6.3/10EPSS 0.34%

Last modified

CVE-2026-42926 is a medium-severity vulnerability rated 6.3/10 on the CVSS scale. 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.. EPSS estimates a 0.34% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
5.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

CVSS 4.0
6.3/10

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

EPSS Probability
0.34%

25.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
F5Nginx Gateway Fabric>= 1.3.0, <= 1.6.2
F5Nginx Open Source>= 1.29.4, <= 1.30.0
F5Nginx Gateway Fabric>= 2.0.0, <= 2.6.0
F5Nginx Instance Manager>= 2.16.0, <= 2.22.0
F5Nginx Ingress Controller>= 3.5.0, <= 3.7.2
F5Nginx Ingress Controller>= 4.0.0, <= 4.0.1
F5Nginx Ingress Controller>= 5.0.0, <= 5.4.2

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is 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.
How severe is CVE-2026-42926?
CVE-2026-42926 has a CVSS score of 6.3/10 (MEDIUM severity). The EPSS model estimates a 0.34% probability of exploitation in the next 30 days.
How do I fix CVE-2026-42926?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-42926?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST