CVE-2026-9256 (GCVE-0-2026-9256)

Vulnerability from cvelistv5 – Published: 2026-05-22 14:11 – Updated: 2026-05-28 18:20 X_F5
VLAI
Title
NGINX ngx_http_rewrite_module vulnerability
Summary
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. 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. 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:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-122 - Heap-based Buffer Overflow
Assigner
f5
References
Impacted products
Vendor Product Version
F5 NGINX Plus Affected: 37.0 , < 37.0.1.1 (custom)
Affected: R36 , < R36 P5 (custom)
Affected: R32 , < R32 P7 (custom)
Create a notification for this product.
F5 NGINX Open Source Affected: 1.31.0 , < 1.31.1 (custom)
Affected: 1.30.0 , < 1.30.2 (custom)
Affected: 0.1.17 , ≤ 0.9.7 (custom)
Create a notification for this product.
Date Public
2026-05-22 14:00
Credits
"F5 acknowledges Mufeed VH of Winfunc Research, Nebula Security (@nebusecurity), and Vexera AI for bringing this issue to our attention and following the highest standards of coordinated disclosure."
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-9256",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-05-22T00:00:00+00:00",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-05-23T03:55:52.757Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      },
      {
        "providerMetadata": {
          "dateUpdated": "2026-05-23T00:35:26.077Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "http://www.openwall.com/lists/oss-security/2026/05/22/14"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unknown",
          "modules": [
            "ngx_http_rewrite_module"
          ],
          "product": "NGINX Plus",
          "vendor": "F5",
          "versions": [
            {
              "lessThan": "37.0.1.1",
              "status": "affected",
              "version": "37.0",
              "versionType": "custom"
            },
            {
              "lessThan": "R36 P5",
              "status": "affected",
              "version": "R36",
              "versionType": "custom"
            },
            {
              "lessThan": "R32 P7",
              "status": "affected",
              "version": "R32",
              "versionType": "custom"
            }
          ]
        },
        {
          "defaultStatus": "unaffected",
          "modules": [
            "ngx_http_rewrite_module"
          ],
          "product": "NGINX Open Source",
          "vendor": "F5",
          "versions": [
            {
              "lessThan": "1.31.1",
              "status": "affected",
              "version": "1.31.0",
              "versionType": "custom"
            },
            {
              "lessThan": "1.30.2",
              "status": "affected",
              "version": "1.30.0",
              "versionType": "custom"
            },
            {
              "lessThanOrEqual": "0.9.7",
              "status": "affected",
              "version": "0.1.17",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "reporter",
          "value": "\"F5 acknowledges Mufeed VH of Winfunc Research, Nebula Security (@nebusecurity), and Vexera AI for bringing this issue to our attention and following the highest standards of coordinated disclosure.\""
        }
      ],
      "datePublic": "2026-05-22T14:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "supportingMedia": [
            {
              "base64": false,
              "type": "text/html",
              "value": "NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. \n\n\nNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated."
            }
          ],
          "value": "NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. 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\n\nNote: 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": "PRESENT",
            "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:P/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": "2026-05-28T18:20:47.449Z",
        "orgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
        "shortName": "f5"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://my.f5.com/manage/s/article/K000161377"
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "tags": [
        "x_F5"
      ],
      "title": "NGINX ngx_http_rewrite_module vulnerability",
      "x_generator": {
        "engine": "F5 SIRTBot v1.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "9dacffd4-cb11-413f-8451-fbbfd4ddc0ab",
    "assignerShortName": "f5",
    "cveId": "CVE-2026-9256",
    "datePublished": "2026-05-22T14:11:41.877Z",
    "dateReserved": "2026-05-21T20:58:58.484Z",
    "dateUpdated": "2026-05-28T18:20:47.449Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-9256",
      "date": "2026-06-15",
      "epss": "0.00913",
      "percentile": "0.55217"
    },
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CVE Program Container\", \"references\": [{\"url\": \"http://www.openwall.com/lists/oss-security/2026/05/22/14\"}], \"providerMetadata\": {\"orgId\": \"af854a3a-2127-422b-91ae-364da2661108\", \"shortName\": \"CVE\", \"dateUpdated\": \"2026-05-23T00:35:26.077Z\"}}, {\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-9256\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-22T14:50:29.157480Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-22T14:50:32.655Z\"}}], \"cna\": {\"tags\": [\"x_F5\"], \"title\": \"NGINX ngx_http_rewrite_module vulnerability\", \"source\": {\"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"reporter\", \"value\": \"\\\"F5 acknowledges Mufeed VH of Winfunc Research, Nebula Security (@nebusecurity), and Vexera AI for bringing this issue to our attention and following the highest standards of coordinated disclosure.\\\"\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 8.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"HIGH\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}, {\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 9.2, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"CRITICAL\", \"valueDensity\": \"NOT_DEFINED\", \"vectorString\": \"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"attackRequirements\": \"PRESENT\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"HIGH\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"HIGH\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"F5\", \"modules\": [\"ngx_http_rewrite_module\"], \"product\": \"NGINX Plus\", \"versions\": [{\"status\": \"affected\", \"version\": \"37.0\", \"lessThan\": \"37.0.1.1\", \"versionType\": \"custom\"}, {\"status\": \"affected\", \"version\": \"R36\", \"lessThan\": \"R36 P5\", \"versionType\": \"custom\"}, {\"status\": \"affected\", \"version\": \"R32\", \"lessThan\": \"R32 P7\", \"versionType\": \"custom\"}], \"defaultStatus\": \"unknown\"}, {\"vendor\": \"F5\", \"modules\": [\"ngx_http_rewrite_module\"], \"product\": \"NGINX Open Source\", \"versions\": [{\"status\": \"affected\", \"version\": \"1.31.0\", \"lessThan\": \"1.31.1\", \"versionType\": \"custom\"}, {\"status\": \"affected\", \"version\": \"1.30.0\", \"lessThan\": \"1.30.2\", \"versionType\": \"custom\"}, {\"status\": \"affected\", \"version\": \"0.1.17\", \"versionType\": \"custom\", \"lessThanOrEqual\": \"0.9.7\"}], \"defaultStatus\": \"unaffected\"}], \"datePublic\": \"2026-05-22T14:00:00.000Z\", \"references\": [{\"url\": \"https://my.f5.com/manage/s/article/K000161377\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"F5 SIRTBot v1.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. \\n\\n\\nNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. 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\\n\\nNote: Software versions which have reached End of Technical Support (EoTS) are not evaluated.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-122\", \"description\": \"CWE-122 Heap-based Buffer Overflow\"}]}], \"providerMetadata\": {\"orgId\": \"9dacffd4-cb11-413f-8451-fbbfd4ddc0ab\", \"shortName\": \"f5\", \"dateUpdated\": \"2026-05-28T18:20:47.449Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-9256\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-28T18:20:47.449Z\", \"dateReserved\": \"2026-05-21T20:58:58.484Z\", \"assignerOrgId\": \"9dacffd4-cb11-413f-8451-fbbfd4ddc0ab\", \"datePublished\": \"2026-05-22T14:11:41.877Z\", \"assignerShortName\": \"f5\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




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.