CVE-2026-40701
CVE-2026-40701 is a medium-severity vulnerability in F5 Dos with a CVSS 3.x base score of 4.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-416.
Key facts
- Severity: Medium (CVSS 3.x base score 4.8)
- CVSS v4: 6.3
- EPSS exploit prediction: 1% (48th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-29981
- Weakness: CWE-416
- Affected product: F5 Dos
- Published:
- Last modified:
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.
Frequently asked questions
- What is CVE-2026-40701?
- 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.
- How severe is CVE-2026-40701?
- CVE-2026-40701 has a CVSS 3.x base score of 4.8, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability low.
- Is CVE-2026-40701 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (48th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-40701?
- CVE-2026-40701 primarily affects F5 Dos. In total, 8 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2026-40701?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-40701 have an EU (EUVD) identifier?
- Yes. CVE-2026-40701 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-29981.
- When was CVE-2026-40701 published?
- CVE-2026-40701 was published on 2026-05-13 and last updated on 2026-06-23.
References
Affected products (8)
- cpe:2.3:a:f5:dos:*:*:*:*:*:nginx:*:*
- cpe:2.3:a:f5:dos:4.8.0:*:*:*:*:nginx:*:*
- cpe:2.3:a:f5:nginx_gateway_fabric:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_ingress_controller:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_instance_manager:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_open_source:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:waf:*:*:*:*:*:nginx:*:*
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