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CVE-2026-42533 (GCVE-0-2026-42533)

Vulnerability from cvelistv5 – Published: 2026-07-15 14:33 – Updated: 2026-07-29 03:55
VLAI
Title
NGINX Map directive and Regex matching vulnerability
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.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
9.2 (Critical)
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
SSVC
Exploitation: poc Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-07-15 00:00 UTC
CWE
  • CWE-122 - Heap-based Buffer Overflow
Assigner
References
URL Tags
https://my.f5.com/manage/s/article/K000162097 vendor-advisorypatch
Impacted products
Vendor Product Version CPE status
F5 NGINX Plus Affected: 37.0.0.1 , < 37.0.3.1 (custom)
Affected: R36 , < R36 P7 (custom)
Affected: R33 , < * (custom)
guessed Create a notification for this product.
F5 NGINX Open Source Affected: 1.31.2 , < 1.31.3 (custom)
Affected: 0.9.6 , < 1.30.4 (custom)
guessed Create a notification for this product.
Date Public
2026-07-15 14:00
Credits
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.
Show details on NVD website
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            ],
            "url": "https://my.f5.com/manage/s/article/K000162097"
          }
        ],
        "sourceIdentifier": "f5sirt@f5.com",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-122"
              }
            ],
            "source": "f5sirt@f5.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Important",
      "current_release_date": "2026-09-14T17:30:58+00:00",
      "cve": "CVE-2026-42533",
      "id": "CVE-2026-42533",
      "initial_release_date": "2026-07-15T14:33:45.810000+00:00",
      "product_status:fixed": "395",
      "product_status:known_affected": "1",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "nginx: NGINX: Arbitrary code execution via crafted HTTP requests",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42533.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-11T16:32:10Z",
      "cve": "CVE-2026-42533",
      "id": "CVE-2026-42533",
      "initial_release_date": "2026-07-16T18:03:02Z",
      "product_status:known_affected": "24",
      "product_status:recommended": "52",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-42533",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-42533.json",
      "version": "8"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-42533",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "total"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-07-15T15:37:45.453471Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-07-15T15:37:52.337Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unknown",
              "modules": [
                "map directive with regex matching"
              ],
              "product": "NGINX Plus",
              "vendor": "F5",
              "versions": [
                {
                  "lessThan": "37.0.3.1",
                  "status": "affected",
                  "version": "37.0.0.1",
                  "versionType": "custom"
                },
                {
                  "lessThan": "R36 P7",
                  "status": "affected",
                  "version": "R36",
                  "versionType": "custom"
                },
                {
                  "lessThan": "*",
                  "status": "affected",
                  "version": "R33",
                  "versionType": "custom"
                }
              ]
            },
            {
              "defaultStatus": "unknown",
              "modules": [
                "map directive with regex matching"
              ],
              "product": "NGINX Open Source",
              "vendor": "F5",
              "versions": [
                {
                  "lessThan": "1.31.3",
                  "status": "affected",
                  "version": "1.31.2",
                  "versionType": "custom"
                },
                {
                  "lessThan": "1.30.4",
                  "status": "affected",
                  "version": "0.9.6",
                  "versionType": "custom"
                }
              ]
            }
          ],
          "credits": [
            {
              "lang": "en",
              "type": "reporter",
              "value": "F5 acknowledges Ming Xuan, DKD (@pidifn), Ji\u0027an 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 T\u00fcrkiye, 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."
            }
          ],
          "datePublic": "2026-07-15T14:00:00.000Z",
          "descriptions": [
            {
              "lang": "en",
              "supportingMedia": [
                {
                  "base64": false,
                  "type": "text/html",
                  "value": "\u003cp\u003eA vulnerability exists in NGINX Plus and NGINX Open Source when a \u003cstrong\u003emap\u003c/strong\u003e\u0026nbsp;directive uses regex matching and a string expression references the map\u0027s 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.\u003c/p\u003eImpact:\u003cbr\u003eThis 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.\u003cbr\u003e\n\n\n\u003cbr\u003e\u0026nbsp;Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated."
                }
              ],
              "value": "A vulnerability exists in NGINX Plus and NGINX Open Source when a map\u00a0directive uses regex matching and a string expression references the map\u0027s 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\u00a0Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "attackComplexity": "HIGH",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.1,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            },
            {
              "cvssV4_0": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "HIGH",
                "attackRequirements": "NONE",
                "attackVector": "NETWORK",
                "baseScore": 9.2,
                "baseSeverity": "CRITICAL",
                "privilegesRequired": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "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",
                "version": "4.0",
                "vulnAvailabilityImpact": "HIGH",
                "vulnConfidentialityImpact": "HIGH",
                "vulnIntegrityImpact": "HIGH",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "format": "CVSS",
              "scenarios": [
                {
                  "lang": "en",
                  "value": "GENERAL"
                }
              ]
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-122",
                  "description": "CWE-122 Heap-based Buffer Overflow",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-07-15T21:20:26.156Z",
            "orgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
            "shortName": "f5"
          },
          "references": [
            {
              "tags": [
                "vendor-advisory",
                "patch"
              ],
              "url": "https://my.f5.com/manage/s/article/K000162097"
            }
          ],
          "source": {
            "discovery": "EXTERNAL"
          },
          "title": "NGINX Map directive and Regex matching vulnerability",
          "x_generator": {
            "engine": "F5 SIRTBot v1.0"
          }
        }
      },
      "cveMetadata": {
        "assignerOrgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
        "assignerShortName": "f5",
        "cveId": "CVE-2026-42533",
        "datePublished": "2026-07-15T14:33:45.810Z",
        "dateReserved": "2026-05-05T21:19:09.517Z",
        "dateUpdated": "2026-07-29T03:55:24.843Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.