CVE-2026-56434
CVE-2026-56434 is a medium-severity vulnerability in F5 Nginx Gateway Fabric with a CVSS 3.x base score of 6.5. 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 6.5)
- CVSS v4: 8.3
- EPSS exploit prediction: 0% (38th percentile)
- Actively exploited: Not listed in CISA KEV
- Weakness: CWE-416
- Affected product: F5 Nginx Gateway Fabric
- Published:
- Last modified:
Description
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuration, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to cause a use-after-free in the NGINX worker process. This issue may lead to limited modification of memory or a restart of the NGINX worker process. Impact: This vulnerability may allow remote attackers to have limited control to modify memory contents or restart the NGINX worker process. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
Frequently asked questions
- What is CVE-2026-56434?
- NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_ssi_module module. This vulnerability may exist when the Server-Side Includes (SSI), proxy_pass, and proxy_buffering off directives are configured. With this configuration, an unauthenticated attacker with man-in-the-middle (MITM) ability to control responses from an upstream server may be able to cause a use-after-free in the NGINX worker process. This issue may lead to limited modification of memory or a restart of the NGINX worker process. Impact: This vulnerability may allow remote attackers to have limited control to modify memory contents or restart the NGINX worker process. There is no control plane exposure; this is a data plane issue only. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
- How severe is CVE-2026-56434?
- CVE-2026-56434 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability high.
- Is CVE-2026-56434 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (38th percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-56434?
- CVE-2026-56434 primarily affects F5 Nginx Gateway Fabric. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
- How do I fix CVE-2026-56434?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- When was CVE-2026-56434 published?
- CVE-2026-56434 was published on 2026-07-15 and last updated on 2026-08-10.
References
Affected products (14)
- cpe:2.3:a:f5:nginx_gateway_fabric:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_ingress_controller:*:*:*:*:continuous_releases:*:*:*
- cpe:2.3:a:f5:nginx_ingress_controller:*:*:*:*:long-term_support:*:*:*
- cpe:2.3:a:f5:nginx_ingress_controller:4.0.0:*:*:*:continuous_releases:*:*:*
- cpe:2.3:a:f5:nginx_ingress_controller:4.0.1:*:*:*:continuous_releases:*:*:*
- cpe:2.3:a:f5:nginx_plus:*:*:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:-:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:p1:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:p2:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:p3:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:p4:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:p5:*:*:*:*:*:*
- cpe:2.3:a:f5:nginx_plus:r36:p6:*:*:*:*:*:*
- cpe:2.3:a:f5:waf:*:*:*:*:*:nginx:*:*
More vulnerabilities in F5 Nginx Gateway Fabric
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- CVE-2026-50107 — High (CVSS 8.1): When NGINX Plus or NGINX Open Source is configured as the data plane for NGINX Gateway Fabric, an injection…
- CVE-2026-42530 — High (CVSS 8.1): NGINX Open Source has a vulnerability in the ngx_http_v3_module module. When NGINX Open Source is configured to use…
- CVE-2026-42055 — High (CVSS 8.1): NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and…
- CVE-2026-11311 — High (CVSS 8.1): When NGINX Plus is configured as the data plane for NGINX Gateway Fabric, an injection vulnerability exists in the…
All CVEs affecting F5 Nginx Gateway Fabric →
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