USN-8563-1: nginx vulnerabilities

unknownpublic exploitCVE-2026-42533 CVE-2026-56434 CVE-2026-60005

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)

CSIRTS triage

vendor: nginx product: nginx Denial of service Remote code execution Information disclosure

What: nginx has vulnerabilities that can lead to denial of service, remote code execution, and information disclosure.
Who is affected: Users of nginx configured with specific modules and directives.
Urgency: Remediation is critical due to the potential for service disruption and exploitation.
Action: Users should update nginx to the latest version.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Ubuntu Security Notices (INTL · vendor-psirt · site)
Severity: unknown
Published: 2026-07-20
Exploitation: Not in CISA KEV at last sync

Original advisory: https://ubuntu.com/security/notices/USN-8563-1

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.

Moderate exploitation riskCVE-2026-425333.6% 30-day exploitation probability. Patch within normal cadence, watch for KEV listing. Riskier than 88% of all scored CVEs.
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.
Low exploitation riskCVE-2026-600050.71% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 50% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-42533	coverage & exploitation status	NVD · CVE.org
CVE-2026-56434	coverage & exploitation status	NVD · CVE.org
CVE-2026-60005	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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