CVE-2026-42944 (GCVE-0-2026-42944)

Vulnerability from cvelistv5 – Published: 2026-05-20 09:20 – Updated: 2026-06-30 12:08
VLAI
Title
Heap overflow with multiple NSID, COOKIE, PADDING EDNS options
Summary
NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options ('nsid', 'answer-cookie', 'pad-responses' (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.
Severity
8.7 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Red
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
Assigner
References
Impacted products
Date Public
2026-05-20 00:00
Credits
Qifan Zhang (Palo Alto Networks)
Show details on NVD website
To clipboard 

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      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-42944\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"yes\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-05-20T13:37:32.347565Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-05-20T13:37:37.199Z\"}}], \"cna\": {\"title\": \"Heap overflow with multiple NSID, COOKIE, PADDING EDNS options\", \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Qifan Zhang (Palo Alto Networks)\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"version\": \"4.0\", \"baseScore\": 8.7, \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Red\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"NLnet Labs\", \"product\": \"Unbound\", \"versions\": [{\"status\": \"affected\", \"version\": \"1.14.0\", \"lessThan\": \"1.25.1\", \"versionType\": \"semver\"}], \"defaultStatus\": \"unaffected\"}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2026-04-26T00:00:00.000Z\", \"value\": \"Issue reported by Qifan Zhang\"}, {\"lang\": \"en\", \"time\": \"2026-04-28T00:00:00.000Z\", \"value\": \"NLnet Labs shares patch\"}, {\"lang\": \"en\", \"time\": \"2026-04-29T00:00:00.000Z\", \"value\": \"Qifan Zhang verifies patch\"}, {\"lang\": \"en\", \"time\": \"2026-05-20T00:00:00.000Z\", \"value\": \"Fixes released with version 1.25.1\"}], \"solutions\": [{\"lang\": \"en\", \"value\": \"This issue is fixed starting with version 1.25.1\"}], \"datePublic\": \"2026-05-20T00:00:00.000Z\", \"references\": [{\"url\": \"https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-42944.txt\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"NLnet Labs Unbound 1.14.0 up to and including version 1.25.0 has a vulnerability that results in heap overflow when encoding multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options in the reply packet. The relevant options (\u0027nsid\u0027, \u0027answer-cookie\u0027, \u0027pad-responses\u0027 (default)) need to be enabled for the vulnerability to be exploited. An adversary who can query Unbound can exploit the vulnerability by attaching multiple NSID and/or DNS Cookie EDNS and/or EDNS Padding options to the query. A flaw in the size calculation of the EDNS field truncates the correct value which allows the encoder to overflow the available space when writing. Those two combined lead to a heap overflow write of Unbound controlled data and eventually a crash. Unbound 1.25.1 contains a patch with a fix to de-duplicate the EDNS options and a fix to prevent truncation of the EDNS field size calculation.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-197\", \"description\": \"CWE-197: Numeric Truncation Error\"}, {\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-787\", \"description\": \"CWE-787: Out-of-bounds Write\"}]}], \"providerMetadata\": {\"orgId\": \"206fc3a0-e175-490b-9eaa-a5738056c9f6\", \"shortName\": \"NLnet Labs\", \"dateUpdated\": \"2026-05-20T09:20:23.906Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-42944\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-20T13:38:17.529Z\", \"dateReserved\": \"2026-05-07T10:07:51.833Z\", \"assignerOrgId\": \"206fc3a0-e175-490b-9eaa-a5738056c9f6\", \"datePublished\": \"2026-05-20T09:20:23.906Z\", \"assignerShortName\": \"NLnet Labs\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


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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.