CVE-2026-88831 (GCVE-0-2026-88831)

Vulnerability from cvelistv5 – Published: 2026-09-23 17:45 – Updated: 2026-09-25 22:28
VLAI
Title
Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths
Summary
BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-23 18:08 UTC
CWE
  • CWE-636 - Not Failing Securely ('Failing Open')
Assigner
redhat CNA under the redhat root
CNA scorecard B 82/100 over 1082 records in the last 180 days details
References
URL Tags
https://access.redhat.com/errata/RHSA-2026:72111 vendor-advisoryx_refsource_REDHAT
https://access.redhat.com/security/cve/CVE-2026-88831 vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2531346 issue-trackingx_refsource_REDHAT
Impacted products
Vendor Product Version CPE status
Red Hat Red Hat Hardened Images Unaffected: 1.37.0-9.1.hum1 , < * (rpm)
    cpe:/a:redhat:hummingbird:1
Create a notification for this product.
Date Public
2026-09-23 16:35
Credits
Red Hat would like to thank Shubham Raj (Causal Security) for reporting this issue.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-88831",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-23T18:08:33.797869Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-23T18:11:48.288Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "collectionURL": "https://catalog.redhat.com/software/containers/",
          "cpes": [
            "cpe:/a:redhat:hummingbird:1"
          ],
          "defaultStatus": "affected",
          "packageName": "busybox-main",
          "product": "Red Hat Hardened Images",
          "vendor": "Red Hat",
          "versions": [
            {
              "lessThan": "*",
              "status": "unaffected",
              "version": "1.37.0-9.1.hum1",
              "versionType": "rpm"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "Red Hat would like to thank Shubham Raj (Causal Security) for reporting this issue."
        }
      ],
      "datePublic": "2026-09-23T16:35:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients."
        }
      ],
      "metrics": [
        {
          "other": {
            "content": {
              "namespace": "https://access.redhat.com/security/updates/classification/",
              "value": "Moderate"
            },
            "type": "Red Hat severity rating"
          }
        },
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
            "version": "3.1"
          },
          "format": "CVSS"
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-636",
              "description": "Not Failing Securely (\u0027Failing Open\u0027)",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T22:28:19.246Z",
        "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
        "shortName": "redhat"
      },
      "references": [
        {
          "name": "RHSA-2026:72111",
          "tags": [
            "vendor-advisory",
            "x_refsource_REDHAT"
          ],
          "url": "https://access.redhat.com/errata/RHSA-2026:72111"
        },
        {
          "tags": [
            "vdb-entry",
            "x_refsource_REDHAT"
          ],
          "url": "https://access.redhat.com/security/cve/CVE-2026-88831"
        },
        {
          "name": "RHBZ#2531346",
          "tags": [
            "issue-tracking",
            "x_refsource_REDHAT"
          ],
          "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2531346"
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-09-09T00:00:00.000Z",
          "value": "Reported to Red Hat."
        },
        {
          "lang": "en",
          "time": "2026-09-23T16:35:00.000Z",
          "value": "Made public."
        }
      ],
      "title": "Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths",
      "workarounds": [
        {
          "lang": "en",
          "value": "Audit all BusyBox httpd configuration files for syntactically valid CIDR prefix lengths. Implement network-level access controls (iptables/nftables) as the primary enforcement layer rather than relying on application-level ACLs."
        }
      ],
      "x_generator": {
        "engine": "cvelib 1.8.0"
      },
      "x_redhatCweChain": "CWE-636: Not Failing Securely (\u0027Failing Open\u0027)"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
    "assignerShortName": "redhat",
    "cveId": "CVE-2026-88831",
    "datePublished": "2026-09-23T17:45:23.299Z",
    "dateReserved": "2026-09-10T09:42:04.559Z",
    "dateUpdated": "2026-09-25T22:28:19.246Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-88831",
      "date": "2026-11-01",
      "epss": "0.00237",
      "percentile": "0.14724"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "collectionURL": "https://catalog.redhat.com/software/containers/",
                "cpes": [
                  "cpe:/a:redhat:hummingbird:1"
                ],
                "defaultStatus": "affected",
                "packageName": "busybox-main",
                "product": "Red Hat Hardened Images",
                "vendor": "Red Hat",
                "versions": [
                  {
                    "lessThan": "*",
                    "status": "unaffected",
                    "version": "1.37.0-9.1.hum1",
                    "versionType": "rpm"
                  }
                ]
              }
            ],
            "source": "secalert@redhat.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients."
          }
        ],
        "id": "CVE-2026-88831",
        "lastModified": "2026-09-25T23:16:54.457",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 5.3,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "LOW",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 1.4,
              "source": "secalert@redhat.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-88831",
                "options": [
                  {
                    "exploitation": "none"
                  },
                  {
                    "automatable": "yes"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-23T18:08:33.797869Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-09-23T18:17:10.080",
        "references": [
          {
            "source": "secalert@redhat.com",
            "url": "https://access.redhat.com/errata/RHSA-2026:72111"
          },
          {
            "source": "secalert@redhat.com",
            "url": "https://access.redhat.com/security/cve/CVE-2026-88831"
          },
          {
            "source": "secalert@redhat.com",
            "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2531346"
          }
        ],
        "sourceIdentifier": "secalert@redhat.com",
        "vulnStatus": "Awaiting Analysis",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-636"
              }
            ],
            "source": "secalert@redhat.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-25T22:28:14+00:00",
      "cve": "CVE-2026-88831",
      "id": "CVE-2026-88831",
      "initial_release_date": "2026-09-23T16:35:00+00:00",
      "product_status:fixed": "7",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "busybox: busybox: httpd silently fails open when IP deny rules contain invalid CIDR prefix lengths",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-88831.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-88831",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "yes"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-09-23T18:08:33.797869Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-09-23T18:10:58.581Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "collectionURL": "https://access.redhat.com/downloads/content/package-browser/",
              "cpes": [
                "cpe:/a:redhat:hummingbird:1"
              ],
              "defaultStatus": "affected",
              "packageName": "busybox",
              "product": "Red Hat Hardened Images",
              "vendor": "Red Hat"
            }
          ],
          "datePublic": "2026-09-23T16:35:00.000Z",
          "descriptions": [
            {
              "lang": "en",
              "value": "BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients."
            }
          ],
          "metrics": [
            {
              "other": {
                "content": {
                  "namespace": "https://access.redhat.com/security/updates/classification/",
                  "value": "Moderate"
                },
                "type": "Red Hat severity rating"
              }
            },
            {
              "cvssV3_1": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "NONE",
                "baseScore": 5.3,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "LOW",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
                "version": "3.1"
              },
              "format": "CVSS"
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-636",
                  "description": "Not Failing Securely (\u0027Failing Open\u0027)",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-09-23T17:45:23.299Z",
            "orgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
            "shortName": "redhat"
          },
          "references": [
            {
              "tags": [
                "vdb-entry",
                "x_refsource_REDHAT"
              ],
              "url": "https://access.redhat.com/security/cve/CVE-2026-88831"
            },
            {
              "name": "RHBZ#2531346",
              "tags": [
                "issue-tracking",
                "x_refsource_REDHAT"
              ],
              "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2531346"
            }
          ],
          "timeline": [
            {
              "lang": "en",
              "time": "2026-09-09T00:00:00.000Z",
              "value": "Reported to Red Hat."
            },
            {
              "lang": "en",
              "time": "2026-09-23T16:35:00.000Z",
              "value": "Made public."
            }
          ],
          "title": "Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths",
          "workarounds": [
            {
              "lang": "en",
              "value": "Audit all BusyBox httpd configuration files for syntactically valid CIDR prefix lengths. Implement network-level access controls (iptables/nftables) as the primary enforcement layer rather than relying on application-level ACLs."
            }
          ],
          "x_generator": {
            "engine": "cvelib 1.8.0"
          },
          "x_redhatCweChain": "CWE-636: Not Failing Securely (\u0027Failing Open\u0027)"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "53f830b8-0a3f-465b-8143-3b8a9948e749",
        "assignerShortName": "redhat",
        "cveId": "CVE-2026-88831",
        "datePublished": "2026-09-23T17:45:23.299Z",
        "dateReserved": "2026-09-10T09:42:04.559Z",
        "dateUpdated": "2026-09-23T18:11:48.288Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    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.