FKIE_CVE-2026-5947

Vulnerability from fkie_nvd - Published: 2026-05-20 13:16 - Updated: 2026-05-21 15:24
Severity ?
7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Summary
Undefined behavior may result due to a race condition leading to a use-after-free violation. If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature. If, during that validation, the "recursive-clients" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message. This issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1. BIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected.
References
security-officer@isc.orghttps://downloads.isc.org/isc/bind9/9.20.23Patch
security-officer@isc.orghttps://downloads.isc.org/isc/bind9/9.21.22Patch
security-officer@isc.orghttps://kb.isc.org/docs/cve-2026-5947Vendor Advisory
Impacted products
Vendor Product Version
isc bind *
isc bind *
To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:isc:bind:*:*:*:*:-:*:*:*",
              "matchCriteriaId": "D92461F1-BA01-479E-B740-38855CC216E6",
              "versionEndExcluding": "9.20.23",
              "versionStartIncluding": "9.20.0",
              "vulnerable": true
            },
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          "operator": "OR"
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  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Undefined behavior may result due to a race condition leading to a use-after-free violation.  If BIND receives an incoming DNS message signed with SIG(0), it begins work to validate that signature.  If, during that validation, the \"recursive-clients\" limit is reached (as would occur during a query flood), and that same DNS message is discarded per the limit, there is a brief window of time while the SIG(0) validation may attempt to read the now-discarded DNS message.\nThis issue affects BIND 9 versions 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, and 9.20.9-S1 through 9.20.22-S1.\nBIND 9 versions 9.18.28 through 9.18.49 and 9.18.28-S1 through 9.18.49-S1 are NOT affected."
    }
  ],
  "id": "CVE-2026-5947",
  "lastModified": "2026-05-21T15:24:32.997",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
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        "impactScore": 3.6,
        "source": "security-officer@isc.org",
        "type": "Secondary"
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          "attackComplexity": "HIGH",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 5.9,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "NONE",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "version": "3.1"
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        "exploitabilityScore": 2.2,
        "impactScore": 3.6,
        "source": "nvd@nist.gov",
        "type": "Primary"
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  "published": "2026-05-20T13:16:40.303",
  "references": [
    {
      "source": "security-officer@isc.org",
      "tags": [
        "Patch"
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      "url": "https://downloads.isc.org/isc/bind9/9.20.23"
    },
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      "source": "security-officer@isc.org",
      "tags": [
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      "url": "https://downloads.isc.org/isc/bind9/9.21.22"
    },
    {
      "source": "security-officer@isc.org",
      "tags": [
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      ],
      "url": "https://kb.isc.org/docs/cve-2026-5947"
    }
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  "sourceIdentifier": "security-officer@isc.org",
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "description": [
        {
          "lang": "en",
          "value": "CWE-362"
        },
        {
          "lang": "en",
          "value": "CWE-416"
        }
      ],
      "source": "security-officer@isc.org",
      "type": "Secondary"
    }
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}


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Sightings

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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.
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  • 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.



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