Vulnerability-Lookup

GHSA-HPR4-88JH-4PVX

Vulnerability from github – Published: 2026-07-22 15:31 – Updated: 2026-07-22 15:31

Details

In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the 'dnscrypt:' clause lists more 'dnscrypt-provider-cert:' files than there are matching 'dnscrypt-secret-key:' files, Unbound fills only the matched prefix and leaves the tail slots at the '0xdb' fill that libsodium's allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with '0xdb' bytes. Any unauthenticated client that sends one UDP datagram of ≥ 68 bytes whose first 8 bytes are '0xdb' to 'dnscrypt-port' will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support ('--enable-dnscrypt').

Severity

5.9 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-55990"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-457"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-07-22T14:17:21Z",
    "severity": "MODERATE"
  },
  "details": "In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0027dnscrypt:\u0027 clause lists more \u0027dnscrypt-provider-cert:\u0027 files than there are matching \u0027dnscrypt-secret-key:\u0027 files, Unbound fills only the matched prefix and leaves the tail slots at the \u00270xdb\u0027 fill that libsodium\u0027s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u00270xdb\u0027 bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u00270xdb\u0027 to \u0027dnscrypt-port\u0027 will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0027--enable-dnscrypt\u0027).",
  "id": "GHSA-hpr4-88jh-4pvx",
  "modified": "2026-07-22T15:31:25Z",
  "published": "2026-07-22T15:31:25Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-55990"
    },
    {
      "type": "WEB",
      "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55990.txt"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-55990 (GCVE-0-2026-55990)

Vulnerability from cvelistv5 – Published: 2026-07-22 13:10 – Updated: 2026-07-22 14:04

Title

Packet of death for a DNSCrypt misconfigured Unbound

Summary

Severity

5.9 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-457 - Use of Uninitialized Variable

Assigner

NLnet Labs

References

1 reference

URL	Tags
https://www.nlnetlabs.nl/downloads/unbound/CVE-20…	vendor-advisory

Impacted products

1 product

Vendor	Product	Version
NLnet Labs	Unbound	Affected: 1.7.0 , < 1.25.2 (semver)

Date Public

2026-07-22 00:00

Credits

Qifan Zhang (Palo Alto Networks)

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JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-55990",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-22T14:04:13.654490Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-22T14:04:28.690Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Unbound",
          "vendor": "NLnet Labs",
          "versions": [
            {
              "lessThan": "1.25.2",
              "status": "affected",
              "version": "1.7.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Qifan Zhang (Palo Alto Networks)"
        }
      ],
      "datePublic": "2026-07-22T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "In NLnet Labs Unbound 1.7.0 up to and including 1.25.1, when the \u0027dnscrypt:\u0027 clause lists more \u0027dnscrypt-provider-cert:\u0027 files than there are matching \u0027dnscrypt-secret-key:\u0027 files, Unbound fills only the matched prefix and leaves the tail slots at the \u00270xdb\u0027 fill that libsodium\u0027s allocator writes into every allocation. Unbound would then iterate over the number of cert files, not the actual slots, so it walks into a slot with garbage data filled with \u00270xdb\u0027 bytes. Any unauthenticated client that sends one UDP datagram of \u2265 68 bytes whose first 8 bytes are \u00270xdb\u0027 to \u0027dnscrypt-port\u0027 will use that garbage entry which leads to a garbage dereference killing the server. This is a silent faulty configuration that goes unnoticed until triggered with the right client query. Unbound needs to be compiled with DNSCrypt support (\u0027--enable-dnscrypt\u0027)."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 5.9,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "Unbound configured with DNSCrypt support (\u0027--enable-dnscrypt\u0027)"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-457",
              "description": "CWE-457: Use of Uninitialized Variable",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-22T13:10:01.635Z",
        "orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
        "shortName": "NLnet Labs"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-55990.txt"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "This issue is fixed starting with version 1.25.2"
        }
      ],
      "timeline": [
        {
          "lang": "en",
          "time": "2026-05-18T00:00:00.000Z",
          "value": "Issue reported by Qifan Zhang"
        },
        {
          "lang": "en",
          "time": "2026-06-10T00:00:00.000Z",
          "value": "NLnet Labs shares patch"
        },
        {
          "lang": "en",
          "time": "2026-06-13T00:00:00.000Z",
          "value": "Qifan Zhang verifies patch"
        },
        {
          "lang": "en",
          "time": "2026-07-22T00:00:00.000Z",
          "value": "Fixes released with version 1.25.2"
        }
      ],
      "title": "Packet of death for a DNSCrypt misconfigured Unbound",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6",
    "assignerShortName": "NLnet Labs",
    "cveId": "CVE-2026-55990",
    "datePublished": "2026-07-22T13:10:01.635Z",
    "dateReserved": "2026-06-22T10:11:10.529Z",
    "dateUpdated": "2026-07-22T14:04:28.690Z",
    "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.

Action not permitted

GHSA-HPR4-88JH-4PVX

CVE-2026-55990 (GCVE-0-2026-55990)

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Sightings

Nomenclature