USN-8563-4

USN-8563-3 fixed a vulnerability in nginx. The fix introduced a regression in certain environments. This update reverts the fix for CVE-2026-42533 pending further investigation.

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Original advisory details:

It was discovered that nginx incorrectly handled certain map directives using regex matching and capture variables. A remote attacker could use this issue to cause nginx to crash, resulting in a denial of service, or possibly execute arbitrary code. (CVE-2026-42533)

It was discovered that nginx had a use-after-free vulnerability in the ngx_http_ssi_module module when configured with Server-Side Includes, proxy_pass, and proxy buffering disabled directives. An attacker able to intercept traffic and control responses from an upstream server could possibly use this issue to cause nginx to crash, resulting in a denial of service. (CVE-2026-56434)

It was discovered that nginx incorrectly handled certain requests in the ngx_http_slice_module module. A remote attacker could possibly use this issue to obtain sensitive information or cause nginx to crash, resulting in a denial of service. (CVE-2026-60005)