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{"bugzilla": {"description": "nginx: ngx_http_rewrite_module: code execution and denial of service", "id": "2480746", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2480746"}, "csaw": false, "cvss3": {"cvss3_base_score": "8.1", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H", "status": "draft"}, "cwe": "CWE-122", "details": ["A flaw was found in the ngx_http_rewrite_module module of NGINX. When a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures and a replacement string that references multiple such captures in a redirect or arguments context, an unauthenticated attacker can send crafted HTTP requests and cause a heap-based buffer overflow in the worker process, potentially allowing code execution or a denial of service by forcing the process to restart."], "mitigation": {"lang": "en:us", "value": "To mitigate this vulnerability, use named captures instead of unnamed captures in rewrite definitions.\nFor example, the following rewrite directive uses unnamed PCRE capture groups, $1 and $2:\n~~~\nrewrite ^/users/([0-9]+)/profile/(.*)$ /profile.php?id=$1&tab=$2 last;\n~~~\nTo mitigate this vulnerability for this example, replace $1 and $2 with the appropriate named captures, $user_id and $section:\n~~~\nrewrite ^/users/(?<user_id>[0-9]+)/profile/(?<section>.*)$ /profile.php?id=$user_id&tab=$section last;\n~~~"}, "name": "CVE-2026-9256", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Affected", "package_name": "nginx", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Affected", "package_name": "nginx:1.24/nginx", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "nginx", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "nginx:1.24/nginx", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Affected", "package_name": "nginx:1.26/nginx", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Affected", "package_name": "nginx", "product_name": "Red Hat Hardened Images"}, {"cpe": "cpe:/a:redhat:insights_proxy:1", "fix_state": "Affected", "package_name": "insights-proxy/insights-proxy-container-rhel9", "product_name": "Red Hat Lightspeed proxy 1"}], "public_date": "2026-05-22T14:11:41Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-9256\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-9256\nhttps://my.f5.com/manage/s/article/K000161377"], "statement": "To exploit this vulnerability, a rewrite directive must be configured with a regex pattern that uses distinct, overlapping PCRE captures and a replacement string referencing multiple such captures, limiting its exposure as this is not the default configuration. This issue allows an attacker to potentially execute arbitrary code or cause a denial of service by forcing the worker process to restart.\nDefault Red Hat Enterprise Linux security features, including SELinux enforcement, Address Space Layout Randomization (ASLR) and NX (No-Execute) stack protection, significantly increase the difficulty of achieving arbitrary code execution, limiting the impact of this vulnerability.\nDue to these reasons, this flaw has been rated with an important severity.", "threat_severity": "Important"}