Security advisory
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. 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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-42533
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 06:34 UTC · Revision 1
Source evidence
A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. 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.
osv:CVE-2026-42533
Complete source record
{
"id": "7b8fb88c825e59038b4e01bd060289aa6553e777e23965ed8e9f82ba7bec3bda",
"url": "https://osv.dev/vulnerability/CVE-2026-42533",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2026-42533",
"summary": "A vulnerability exists in NGINX Plus and NGINX Open Source when a map directive uses regex matching and a string expression references the map's regex capture variables before referencing the map output variable. Alternatively, the same result could be achieved by using a non-cacheable variable in a string expression under certain conditions. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Impact: This vulnerability may allow remote attackers to cause a denial-of-service (DoS) on the NGINX system or to possibly trigger a code execution. 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.",
"evidence": "osv:CVE-2026-42533",
"products": [],
"severity": "critical",
"structured": {
"id": "CVE-2026-42533",
"aliases": [
"BIT-nginx-2026-42533",
"BIT-nginx-gateway-2026-42533",
"CVE-2026-42533"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/nginx/nginx-gateway-fabric",
"type": "GIT",
"events": [
{
"introduced": "3a372747333fb1db372af7cf0b18ed7eef7c91f7"
},
{
"last_affected": "532db6a20b2912fe397211eef9f8d564d46a4bdd"
},
{
"introduced": "7dad8b31e3f0c3eadce36fed8c276e83e6583d24"
},
{
"fixed": "5e34a17a8f7787e90f41d1af91258a556f0795b4"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:f5:nginx_gateway_fabric:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "1.3.0"
},
{
"last_affected": "1.6.2"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:f5:nginx_gateway_fabric:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2.0.0"
},
{
"fixed": "2.6.7"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42533.json"
}
}
],
"modified": "2026-10-24T10:30:41.404024020Z",
"provider": "osv",
"references": [
"https://my.f5.com/manage/s/article/K000162097"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:a:f5:nginx_ingress_controller:*:*:*:*:continuous_releases:*:*:*",
"cpe:2.3:a:f5:nginx_ingress_controller:*:*:*:*:long-term_support:*:*:*"
],
"vendor_product": "f5:nginx_ingress_controller",
"extracted_events": [
{
"range": [
{
"introduced": "3.5.0"
},
{
"last_affected": "3.7.2"
},
{
"introduced": "5.0.0"
},
{
"fixed": "5.5.3"
},
{
"introduced": "2026-lts-r1"
},
{
"fixed": "2026-lts-r4"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:a:f5:nginx_plus:*:*:*:*:*:*:*:*"
],
"vendor_product": "f5:nginx_plus",
"extracted_events": [
{
"range": [
{
"introduced": "37.0.0.1"
},
{
"fixed": "37.0.3.1"
},
{
"introduced": "r33"
},
{
"fixed": "r36"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:a:f5:waf:*:*:*:*:*:nginx:*:*"
],
"vendor_product": "f5:waf",
"extracted_events": [
{
"range": [
{
"introduced": "4.11.0"
},
{
"last_affected": "4.16.0"
},
{
"introduced": "5.2.0"
},
{
"last_affected": "5.8.0"
},
{
"introduced": "5.9.0"
},
{
"fixed": "5.13.4"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:a:f5:nginx_ingress_controller:4.0.0:*:*:*:continuous_releases:*:*:*",
"cpe:2.3:a:f5:nginx_ingress_controller:4.0.1:*:*:*:continuous_releases:*:*:*"
],
"vendor_product": "f5:nginx_ingress_controller",
"extracted_events": [
{
"range": [
{
"introduced": "4.0.0"
},
{
"last_affected": "4.0.0"
},
{
"introduced": "4.0.1"
},
{
"last_affected": "4.0.1"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:f5:nginx_plus:r36:-:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_plus:r36:p1:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_plus:r36:p2:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_plus:r36:p3:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_plus:r36:p4:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_plus:r36:p5:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_plus:r36:p6:*:*:*:*:*:*"
],
"vendor_product": "f5:nginx_plus",
"extracted_events": [
{
"range": [
{
"introduced": "r36-NA"
},
{
"last_affected": "r36-NA"
},
{
"introduced": "r36-p1"
},
{
"last_affected": "r36-p1"
},
{
"introduced": "r36-p2"
},
{
"last_affected": "r36-p2"
},
{
"introduced": "r36-p3"
},
{
"last_affected": "r36-p3"
},
{
"introduced": "r36-p4"
},
{
"last_affected": "r36-p4"
},
{
"introduced": "r36-p5"
},
{
"last_affected": "r36-p5"
},
{
"introduced": "r36-p6"
},
{
"last_affected": "r36-p6"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2026-42533",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 435144,
"published_at": "2026-07-15T15:16:33.48+00:00"
}