CVE-2026-42055
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (6.54%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request. This may cause a heap-based buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
- CVSS 4.0
- 9.2 CRITICALCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
- EPSS
- 6.54% probability · 93th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-122, CWE-787, CWE-131
- Affected
- f5/dos · f5/nginx gateway fabric · f5/nginx ingress controller · f5/nginx instance manager · f5/nginx open source · f5/nginx plus · f5/waf · redhat/discovery · redhat/hardened images · redhat/update infrastructure · redhat/enterprise linux
- Source
- f5sirt@f5.com
References
- https://my.f5.com/manage/s/article/K000161584Vendor Advisory
- https://access.redhat.com/errata/RHSA-2026:27197Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:36331Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:36364Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:36618Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:36639Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:38847Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:44481Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:46836Third Party Advisory
- https://access.redhat.com/errata/RHSA-2026:58981
- https://access.redhat.com/security/cve/CVE-2026-42055Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=2489866Issue Tracking, Third Party Advisory
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42055.jsonThird Party Advisory
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.