← Vulnerability feed

Vulnerability record · CVE-2026-40701 · published 13 May 2026

CVE-2026-40701: F5 dos use after free vulnerability

F5 · Dos

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssl_module module when the ssl_verify_client directive is set to "on" or "optional," and the ssl_ocsp directive is set to "on" or the leaf parameters are configured with a resolver. With this configuration, an unauthenticated attacker can send requests along with conditions beyond its control that may cause a heap-use-after-free error in the NGINX worker process. This vulnerability may result in limited modification of data or the NGINX worker process restarting.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

6.3 CVSS 4.0 Medium EPSS 0.34% · top 74.7% CWE-416 · Use after free
6.3CVSS 4.0 base score
0.34%EPSS exploitation probability, 30 days
NoNot in CISA KEV
7Affected product versions listed by NVD
1References
23 Jun 2026Last modified by NVD

Description

NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssl_module module when the ssl_verify_client directive is set to "on" or "optional," and the ssl_ocsp directive is set to "on" or the leaf parameters are configured with a resolver. With this configuration, an unauthenticated attacker can send requests along with conditions beyond its control that may cause a heap-use-after-free error in the NGINX worker process. This vulnerability may result in limited modification of data or the NGINX worker process restarting.  Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/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/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

Affected products

7 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://my.f5.com/manage/s/article/K000161021 MitigationVendor Advisory

Track CVE-2026-40701 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.5CVE-2023-44487HTTP/2 Rapid Reset stream cancellation denial of serviceThe HTTP/2 protocol permits a client to cancel many streams quickly, and the server's handling of those resets consumes disproportionate resources. T…KEVEPSS 100%analysed9.2CVE-2026-42533F5 nginx gateway fabric heap-based buffer overflow vulnerabilityA vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's rege…EPSS 0.89%9.2CVE-2026-42055F5 dos heap-based buffer overflow vulnerabilityNGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists whe…EPSS 2.4%9.2CVE-2026-42530F5 nginx gateway fabric use after free vulnerabilityNGINX Open Source has a vulnerability in the ngx_http_v3_module module. When NGINX Open Source is configured to use the HTTP/3 QUIC module, a remote …EPSS 1.1%9.2CVE-2026-9256F5 nginx open source heap-based buffer overflow vulnerabilityNGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses …EPSS 2.7%9.2CVE-2026-42945NGINX rewrite module heap buffer overflow via crafted HTTP requestsNGINX Plus and NGINX Open Source contain a heap buffer overflow in the ngx_http_rewrite_module when a rewrite directive is followed by another rewrit…EPSS 3.4%analysed8.8CVE-2026-60005F5 nginx gateway fabric use of uninitialized resource vulnerabilityNGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_slice_module module. When the slice directive and unnamed regex captures are co…EPSS 0.53%8.8CVE-2026-27654F5 nginx plus heap-based buffer overflow vulnerabilityNGINX Open Source and NGINX Plus have a vulnerability in the ngx_http_dav_module module that might allow an attacker to trigger a buffer overflow to …EPSS 1.5%

Source: NIST National Vulnerability Database (record CVE-2026-40701), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.