{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-41637", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "state": "PUBLISHED", "assignerShortName": "NLnet Labs", "dateReserved": "2026-06-22T10:11:10.518Z", "datePublished": "2026-07-22T13:04:52.605Z", "dateUpdated": "2026-07-22T14:29:25.088Z"}, "containers": {"cna": {"title": "Degradation of resolution service from improperly accounted client-terminated DNS-over-QUIC queries", "datePublic": "2026-07-22T00:00:00.000Z", "affected": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"version": "1.22.0", "status": "affected", "lessThan": "1.25.2", "versionType": "semver"}], "defaultStatus": "unaffected"}], "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, client terminated DNS-over-QUIC (DoQ) queries are not accounted properly by Unbound resulting in low-cost inflation of the waiting number of replies for already in-flight resolution queries. This results in degradation of resolution service for new clients for already in-flight queries. A malicious actor can exploit the vulnerability by issuing DoQ queries for query names that need resolution and proceeding on immediately terminating the query by one of STOP_SENDING/RESET_STREAM/CONNECTION_CLOSE QUIC frames. Those terminated DoQ queries are not properly counted for and keep inflating the number of waiting replies for in-flight queries. When the maximum is reached, it results in silent query drops for new clients needing resolution for already in-flight queries. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces. Additionally, a malicious actor needs access to multiple source IPs to bypass the by-default configured 'wait-limit' option."}], "metrics": [{"format": "CVSS", "scenarios": [{"lang": "en", "value": "Unbound compiled with DoQ support ('--with-libngtcp2')"}], "cvssV3_1": {"version": "3.1", "baseScore": 3.7, "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"}}], "problemTypes": [{"descriptions": [{"lang": "en", "cweId": "CWE-772", "description": "CWE-772: Missing Release of Resource after Effective Lifetime", "type": "CWE"}]}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.25.2"}], "timeline": [{"time": "2026-05-22T00:00:00.000Z", "lang": "en", "value": "Issue reported by Qifan Zhang"}, {"time": "2026-06-17T00:00:00.000Z", "lang": "en", "value": "NLnet Labs shares patch"}, {"time": "2026-06-17T00:00:00.000Z", "lang": "en", "value": "Qifan Zhang verifies patch"}, {"time": "2026-07-22T00:00:00.000Z", "lang": "en", "value": "Fixes released with version 1.25.2"}], "credits": [{"lang": "en", "value": "Qifan Zhang (Palo Alto Networks)", "type": "finder"}], "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt", "tags": ["vendor-advisory"]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-07-22T13:04:52.605Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-07-22T14:29:10.891526Z", "id": "CVE-2026-41637", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-22T14:29:25.088Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-41637", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "version": "2.0.3", "timestamp": "2026-07-22T14:29:10.891526Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-07-22T14:29:17.367Z"}}], "cna": {"title": "Degradation of resolution service from improperly accounted client-terminated DNS-over-QUIC queries", "credits": [{"lang": "en", "type": "finder", "value": "Qifan Zhang (Palo Alto Networks)"}], "metrics": [{"format": "CVSS", "cvssV3_1": {"version": "3.1", "baseScore": 3.7, "baseSeverity": "LOW", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L"}, "scenarios": [{"lang": "en", "value": "Unbound compiled with DoQ support ('--with-libngtcp2')"}]}], "affected": [{"vendor": "NLnet Labs", "product": "Unbound", "versions": [{"status": "affected", "version": "1.22.0", "lessThan": "1.25.2", "versionType": "semver"}], "defaultStatus": "unaffected"}], "timeline": [{"lang": "en", "time": "2026-05-22T00:00:00.000Z", "value": "Issue reported by Qifan Zhang"}, {"lang": "en", "time": "2026-06-17T00:00:00.000Z", "value": "NLnet Labs shares patch"}, {"lang": "en", "time": "2026-06-17T00:00:00.000Z", "value": "Qifan Zhang verifies patch"}, {"lang": "en", "time": "2026-07-22T00:00:00.000Z", "value": "Fixes released with version 1.25.2"}], "solutions": [{"lang": "en", "value": "This issue is fixed starting with version 1.25.2"}], "datePublic": "2026-07-22T00:00:00.000Z", "references": [{"url": "https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt", "tags": ["vendor-advisory"]}], "x_generator": {"engine": "cvelib 1.8.0"}, "descriptions": [{"lang": "en", "value": "In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, client terminated DNS-over-QUIC (DoQ) queries are not accounted properly by Unbound resulting in low-cost inflation of the waiting number of replies for already in-flight resolution queries. This results in degradation of resolution service for new clients for already in-flight queries. A malicious actor can exploit the vulnerability by issuing DoQ queries for query names that need resolution and proceeding on immediately terminating the query by one of STOP_SENDING/RESET_STREAM/CONNECTION_CLOSE QUIC frames. Those terminated DoQ queries are not properly counted for and keep inflating the number of waiting replies for in-flight queries. When the maximum is reached, it results in silent query drops for new clients needing resolution for already in-flight queries. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces. Additionally, a malicious actor needs access to multiple source IPs to bypass the by-default configured 'wait-limit' option."}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "cweId": "CWE-772", "description": "CWE-772: Missing Release of Resource after Effective Lifetime"}]}], "providerMetadata": {"orgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "shortName": "NLnet Labs", "dateUpdated": "2026-07-22T13:04:52.605Z"}}}, "cveMetadata": {"cveId": "CVE-2026-41637", "state": "PUBLISHED", "dateUpdated": "2026-07-22T14:29:25.088Z", "dateReserved": "2026-06-22T10:11:10.518Z", "assignerOrgId": "206fc3a0-e175-490b-9eaa-a5738056c9f6", "datePublished": "2026-07-22T13:04:52.605Z", "assignerShortName": "NLnet Labs"}, "dataVersion": "5.2"}

{}

{"bugzilla": {"description": "unbound: Unbound: Denial of Service via terminated DNS-over-QUIC queries", "id": "2506143", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2506143"}, "csaw": false, "cvss3": {"cvss3_base_score": "3.7", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-911", "details": ["A flaw was found in Unbound, a Domain Name System (DNS) resolver. A remote attacker can exploit this vulnerability by sending and immediately terminating DNS-over-QUIC (DoQ) queries. This improper handling of terminated queries can lead to a build-up of pending responses, causing a degradation of service for new clients and ultimately a Denial of Service (DoS)."], "mitigation": {"lang": "en:us", "value": "To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration.\nRestart the Unbound service to apply the changes and clear any lingering resource limits."}, "name": "CVE-2026-41637", "package_state": [{"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Affected", "package_name": "unbound", "product_name": "Red Hat Hardened Images"}], "public_date": "2026-07-22T13:04:52Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-41637\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-41637\nhttps://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt"], "statement": "This vulnerability is rated as Low impact. Unbound, as distributed in Red Hat products, is not typically configured with DNS-over-QUIC (DoQ) support enabled by default. Exploitation requires Unbound to be explicitly compiled with `--with-libngtcp2` and have `quic-port` configured, in addition to an attacker bypassing default rate limits with multiple source IPs. This makes successful exploitation difficult in standard Red Hat deployments.", "threat_severity": "Low"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[1.22.0,1.25.2)"}}], "enrichment": {"confidence": 97.0, "confidence_source": "matching", "scores": [{"score": 97.0, "source": "matching"}]}, "original": {"product": "Unbound", "source": "cna", "vendor": "NLnet Labs"}, "product": "unbound", "vendor": "nlnetlabs"}], "created": "2026-07-23T19:00:17.243526+00:00", "updated": "2026-07-30T09:30:15.249226+00:00", "vendors": ["nlnetlabs", "nlnetlabs$PRODUCT$unbound"]}