{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-42533", "assignerOrgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab", "state": "PUBLISHED", "assignerShortName": "f5", "dateReserved": "2026-05-05T21:19:09.517Z", "datePublished": "2026-07-15T14:33:45.810Z", "dateUpdated": "2026-07-29T03:55:24.843Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab", "shortName": "f5", "dateUpdated": "2026-07-15T21:20:26.156Z" }, "title": "NGINX Map directive and Regex matching vulnerability", "datePublic": "2026-07-15T14:00:00.000Z", "problemTypes": [ { "descriptions": [ { "lang": "en", "cweId": "CWE-122", "description": "CWE-122 Heap-based Buffer Overflow", "type": "CWE" } ] } ], "affected": [ { "vendor": "F5", "product": "NGINX Plus", "modules": [ "map directive with regex matching" ], "versions": [ { "status": "affected", "version": "37.0.0.1", "lessThan": "37.0.3.1", "versionType": "custom" }, { "status": "affected", "version": "R36", "lessThan": "R36 P7", "versionType": "custom" }, { "status": "affected", "version": "R33", "lessThan": "*", "versionType": "custom" } ], "defaultStatus": "unknown" }, { "vendor": "F5", "product": "NGINX Open Source", "modules": [ "map directive with regex matching" ], "versions": [ { "status": "affected", "version": "1.31.2", "lessThan": "1.31.3", "versionType": "custom" }, { "status": "affected", "version": "0.9.6", "lessThan": "1.30.4", "versionType": "custom" } ], "defaultStatus": "unknown" } ], "descriptions": [ { "lang": "en", "value": "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.\n\nImpact:\nThis 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.\n\n\n\n\n Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.", "supportingMedia": [ { "type": "text/html", "base64": false, "value": "

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.
\n\n\n
 Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated." } ] } ], "references": [ { "url": "https://my.f5.com/manage/s/article/K000162097", "tags": [ "vendor-advisory", "patch" ] } ], "metrics": [ { "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ], "cvssV3_1": { "version": "3.1", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH", "baseSeverity": "HIGH", "baseScore": 8.1, "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H" } }, { "format": "CVSS", "scenarios": [ { "lang": "en", "value": "GENERAL" } ], "cvssV4_0": { "version": "4.0", "attackVector": "NETWORK", "attackComplexity": "HIGH", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "HIGH", "subConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "subIntegrityImpact": "NONE", "vulnAvailabilityImpact": "HIGH", "subAvailabilityImpact": "NONE", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED", "baseSeverity": "CRITICAL", "baseScore": 9.2, "vectorString": "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" } } ], "credits": [ { "lang": "en", "value": "F5 acknowledges Ming Xuan, DKD (@pidifn), Ji'an Zhou, and Zhen Yan of AntAISecurityLab, Rafael Gacek, Sergii Negodiuk of EVO.company, Lam Jun Rong of Calif.io, Mufeed VH of Winfunc Research (winfunc.com), Vexera AI (https://vexera.ai), Tu Tran Dinh (@1w4y), Stan Shaw (cyberstan), qianshuidewajueji, zenneth (randomguy6407), Zhenpeng (Leo) Lin of depthfirst, Lukas Johannes Moeller, Melih Tolga Sahin of Vodafone Türkiye, Ayoub Nabil Boubagrat (GitHub: @ayoubnabil), and Milan Jovic (Kljunowsky) for independently bringing this issue to our attention and following the highest standards of coordinated disclosure.", "type": "reporter" } ], "source": { "discovery": "EXTERNAL" }, "x_generator": { "engine": "F5 SIRTBot v1.0" } }, "adp": [ { "metrics": [ { "other": { "type": "ssvc", "content": { "timestamp": "2026-07-15T00:00:00+00:00", "options": [ { "Exploitation": "poc" }, { "Automatable": "no" }, { "Technical Impact": "total" } ], "role": "CISA Coordinator", "version": "2.0.3", "id": "CVE-2026-42533" } } } ], "title": "CISA ADP Vulnrichment", "providerMetadata": { "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-29T03:55:24.843Z" } } ] } }