USN-8955-2: nginx vulnerabilities

USN-8955-1 fixed vulnerabilities in nginx in Ubuntu 26.10, Ubuntu 26.04 LTS, Ubuntu 24.04 LTS, and Ubuntu 22.04 LTS. This update provides the corresponding update for Ubuntu 20.04 LTS, Ubuntu 18.04 LTS, Ubuntu 16.04 LTS, and Ubuntu 14.04 LTS.

In addition, this update fixes CVE-2026-42533 for these releases.

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

Original advisory details:

It was discovered that nginx incorrectly handled certain configurations using the alias directive together with rewrite rules. A remote attacker could possibly use this issue to cause nginx to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-15176)

It was discovered that nginx incorrectly handled map directives using regex matching under certain circumstances. A remote attacker could possibly use this issue to cause nginx to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-93479)

It was discovered that nginx incorrectly handled HTTP/3 requests when proxy_request_buffering was enabled. This issue only affected Ubuntu 26.04 LTS and Ubuntu 26.10. A remote attacker could possibly use this issue to inject data into proxied requests. (CVE-2026-95101)

It was discovered that nginx incorrectly handled asynchronous file I/O in certain configurations with Server Side Includes pages. A remote attacker could possibly use this issue to cause nginx to crash, resulting in a denial of service, or execute arbitrary code. (CVE-2026-97205)

It was discovered that nginx incorrectly handled SSL session ticket keys when configured with a shared session cache but without explicit ticket key rotation. This issue only affected Ubuntu 24.04 LTS, Ubuntu 26.04 LTS, and Ubuntu 26.10. A remote attacker could possibly use this issue to forge client SSL sessions and bypass client certificate verification. (CVE-2026-97629)