Vulnerability-Lookup

FKIE_CVE-2026-9256

Vulnerability from fkie_nvd - Published: 2026-05-22 15:16 - Updated: 2026-08-11 14:48

Severity

8.1 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
8.1 (High) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

References

URL	Tags
f5sirt@f5.com	https://my.f5.com/manage/s/article/K000161377	Mitigation, Vendor Advisory
af854a3a-2127-422b-91ae-364da2661108	http://www.openwall.com/lists/oss-security/2026/05/22/14	Mailing List
af854a3a-2127-422b-91ae-364da2661108	https://lists.debian.org/debian-lts-announce/2026/06/msg00023.html	Mailing List, Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:20351	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:28212	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:28921	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:28973	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:29151	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:29874	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:33313	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/errata/RHSA-2026:44481	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://access.redhat.com/security/cve/CVE-2026-9256	Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://bugzilla.redhat.com/show_bug.cgi?id=2480746	Issue Tracking, Third Party Advisory
0b0ca135-0b70-47e7-9f44-1890c2a1c46c	https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-9256.json	Third Party Advisory

Impacted products

Vendor	Product	Version
f5	nginx_open_source	*
f5	nginx_open_source	*
f5	nginx_open_source	1.31.0
f5	nginx_plus	*
f5	nginx_plus	37.0.0.1
f5	nginx_plus	r32
f5	nginx_plus	r32
f5	nginx_plus	r32
f5	nginx_plus	r32
f5	nginx_plus	r32
f5	nginx_plus	r32
f5	nginx_plus	r32
f5	nginx_plus	r36
f5	nginx_plus	r36
f5	nginx_plus	r36
f5	nginx_plus	r36
f5	nginx_plus	r36
f5	dos	*
f5	dos	4.9.0
f5	nginx_gateway_fabric	*
f5	nginx_gateway_fabric	*
f5	nginx_ingress_controller	*
f5	nginx_ingress_controller	*
f5	nginx_ingress_controller	*
f5	nginx_instance_manager	*
f5	waf	*
f5	waf	*
f5	waf	*
redhat	discovery	-
redhat	hardened_images	-
redhat	update_infrastructure	*
debian	debian_linux	11.0
redhat	enterprise_linux	8.0
redhat	enterprise_linux	9.0
redhat	enterprise_linux	10.0

JSON

To clipboard

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

Vulnerability from cvelistv5 – Published: 2026-05-22 14:11 – Updated: 2026-07-24 12:05 X_F5

Title

NGINX ngx_http_rewrite_module vulnerability

Summary

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 · CISA-ADP (v2.0.3)

Decision recorded 2026-05-22 00:00 UTC

CWE

CWE-122 - Heap-based Buffer Overflow

Assigner

f5 mitre root

References

14 references

URL	Tags
https://my.f5.com/manage/s/article/K000161377	vendor-advisory
http://www.openwall.com/lists/oss-security/2026/0…
https://lists.debian.org/debian-lts-announce/2026…
https://access.redhat.com/security/cve/CVE-2026-9256	vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2480746	issue-trackingx_refsource_REDHAT
https://security.access.redhat.com/data/csaf/v2/v…	x_sadp-csaf-vex
https://access.redhat.com/errata/RHSA-2026:29874	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:28921	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:28212	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:28973	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:29151	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:33313	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:20351	vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/errata/RHSA-2026:44481	vendor-advisoryx_refsource_REDHAT

Impacted products

13 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)
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)
Red Hat	Red Hat Enterprise Linux 10	Unaffected: 2:1.26.3-6.el10_2.4 , < * (rpm) cpe:/o:redhat:enterprise_linux:10.2
Red Hat	Red Hat Enterprise Linux 8	Unaffected: 8100020260611094050.489197e6 , < * (rpm) cpe:/a:redhat:enterprise_linux:8
Red Hat	Red Hat Enterprise Linux 9	Unaffected: 9080020260610161820.9 , < * (rpm) cpe:/a:redhat:enterprise_linux:9
Red Hat	Red Hat Enterprise Linux 9	Unaffected: 2:1.20.1-28.el9_8.3 , < * (rpm) cpe:/a:redhat:enterprise_linux:9
Red Hat	Red Hat Enterprise Linux 9	Unaffected: 9080020260609152155.9 , < * (rpm) cpe:/a:redhat:enterprise_linux:9
Red Hat	Red Hat Discovery 2	Unaffected: 1782756541 , < * (rpm) cpe:/a:redhat:discovery:2::el9
Red Hat	Red Hat Hardened Images	Unaffected: 1.30.2-1.hum1 , < * (rpm) cpe:/a:redhat:hummingbird:1
Red Hat	Red Hat Update Infrastructure 5	Unaffected: 1784794818 , < * (rpm) cpe:/a:redhat:rhui:5::el9
Red Hat	Red Hat Update Infrastructure 5	Unaffected: 1784794778 , < * (rpm) cpe:/a:redhat:rhui:5::el9
Red Hat	Red Hat Update Infrastructure 5	Unaffected: 1784795076 , < * (rpm) cpe:/a:redhat:rhui:5::el9
Red Hat	Red Hat Lightspeed proxy 1	cpe:/a:redhat:insights_proxy:1

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

JSON

To clipboard

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              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:29874"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:28921"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:28212"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:28973"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:29151"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:33313"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:20351"
          },
          {
            "tags": [
              "vendor-advisory",
              "x_refsource_REDHAT"
            ],
            "url": "https://access.redhat.com/errata/RHSA-2026:44481"
          }
        ],
        "solutions": [
          {
            "lang": "en",
            "value": "RHSA-2026:29874: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:28921: Red Hat Enterprise Linux AppStream (v. 8)"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:28212: Red Hat Enterprise Linux AppStream (v. 9)"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:28973: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:29151: Red Hat Enterprise Linux AppStream (v. 9)"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:33313: Red Hat Discovery 2"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:20351: Red Hat Hardened Images"
          },
          {
            "lang": "en",
            "value": "RHSA-2026:44481: Red Hat Update Infrastructure 5"
          }
        ],
        "timeline": [
          {
            "lang": "en",
            "time": "2026-05-22T15:00:55.131Z",
            "value": "Reported to Red Hat."
          },
          {
            "lang": "en",
            "time": "2026-05-22T14:11:41.877Z",
            "value": "Made public."
          }
        ],
        "title": "nginx: ngx_http_rewrite_module: code execution and denial of service",
        "workarounds": [
          {
            "lang": "en",
            "value": "To mitigate this vulnerability, use named captures instead of unnamed captures in rewrite definitions.\n\nFor example, the following rewrite directive uses unnamed PCRE capture groups, $1 and $2:\n\n~~~\nrewrite ^/users/([0-9]+)/profile/(.*)$ /profile.php?id=$1\u0026tab=$2 last;\n~~~\n\nTo mitigate this vulnerability for this example, replace $1 and $2 with the appropriate named captures, $user_id and $section:\n\n~~~\nrewrite ^/users/(?\u003cuser_id\u003e[0-9]+)/profile/(?\u003csection\u003e.*)$ /profile.php?id=$user_id\u0026tab=$section last;\n~~~"
          }
        ],
        "x_adpType": "supplier",
        "x_generator": {
          "engine": "sadp-cli 1.0.0"
        }
      }
    ],
    "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": "2026-07-24T12:05:35.262Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

FKIE_CVE-2026-9256

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

Tags

Sightings

Nomenclature