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_buf

mediumCVSS 6.5CVE-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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: medium — CVSS 6.5
Published: 2026-07-15
Last updated: 2026-07-15
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-56434

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-564340.45% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 37% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-56434	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

high[NEW] [high] NGINX NGINX Plus: Multiple vulnerabilitiescert-bund
unknownUSN-8563-2: nginx regressionubuntu
unknownUSN-8563-1: nginx vulnerabilitiesubuntu
unknownMultiple vulnerabilities in F5 products (July 16, 2026)cert-fr-avis
mediumCVE-2026-56434: NGINX ngx_http_ssi_module vulnerabilitymsrc

Recent advisories for NGINX Plus and

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

high[UPDATE] [high] NGINX and NGINX Plus: Multiple vulnerabilitiescert-bund · 2026-07-30
high[NEW] [high] NGINX NGINX Plus: Multiple vulnerabilitiescert-bund · 2026-07-30
high[UPDATE] [high] NGINX Open Source and NGINX Plus: Multiple vulnerabilitiescert-bund · 2026-07-29
high[UPDATE] [high] NGINX and NGINX Plus: Multiple vulnerabilitiescert-bund · 2026-07-24
high[UPDATE] [high] NGINX Open Source and NGINX Plus: Vulnerability allows denial of service and potentially code …cert-bund · 2026-07-24
highCVE-2026-60005: NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_slice_module module. Whe…nvd · 2026-07-15