{
  "threat_severity" : "Important",
  "public_date" : "2026-07-22T00:00:00Z",
  "bugzilla" : {
    "description" : "unbound: Unbound: Denial of Service via improper validation of DNS-over-QUIC client length",
    "id" : "2503060",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=2503060"
  },
  "cvss3" : {
    "cvss3_base_score" : "7.5",
    "cvss3_scoring_vector" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
    "status" : "verified"
  },
  "cwe" : "CWE-770",
  "details" : [ "In NLnet Labs Unbound 1.22.0 up to and including 1.25.1, when downstream DNS-over-QUIC (DoQ) is enabled, the first two bidirectional streams on a new QUIC connection (stream_id 0 and 4) bypass the per-stream 'quic-size' gate entirely, and large input buffers are allocated later, after only the 2-byte length prefix has been received from the initial streams. As a result, a remote client can make Unbound exceed the configured 'quic-size' limit with low-cost input. Using only one connection and two streams, each sending a declared 65535-byte length prefix and then holding the streams open, a client can already trivially make Unbound roughly allocate double that amount. This is a remote availability issue / memory-accounting bypass in the downstream DoQ implementation that leads to denial of service for new DoQ clients. This vulnerability needs Unbound to be compiled with DoQ support ('--with-libngtcp2') and the 'quic-port' to be configured for the listening interfaces.", "A flaw was found in Unbound when DNS-over-QUIC (DoQ) is enabled. An attacker could exploit improper validation of client-provided data length, leading to excessive memory allocation. This can cause the system to exceed its configured memory limits for QUIC connections, resulting in a Denial of Service (DoS) for new DoQ clients." ],
  "statement" : "This Important flaw in Unbound, when configured for DNS-over-QUIC (DoQ), can lead to a denial of service for new DoQ clients. An attacker can exploit improper validation of client-provided data length, causing excessive memory allocation and exceeding configured limits. This impacts the availability of the DNS resolver for DoQ connections.",
  "affected_release" : [ {
    "product_name" : "Red Hat Hardened Images",
    "release_date" : "2026-07-22T00:00:00Z",
    "advisory" : "RHSA-2026:43588",
    "cpe" : "cpe:/a:redhat:hummingbird:1",
    "package" : "unbound-main-1.25.2-0.1.hum1",
    "impact" : "important"
  } ],
  "package_state" : [ {
    "product_name" : "Red Hat Enterprise Linux 10",
    "fix_state" : "Not affected",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:10"
  }, {
    "product_name" : "Red Hat Enterprise Linux 6",
    "fix_state" : "Not affected",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:6"
  }, {
    "product_name" : "Red Hat Enterprise Linux 7",
    "fix_state" : "Not affected",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:7"
  }, {
    "product_name" : "Red Hat Enterprise Linux 8",
    "fix_state" : "Not affected",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:8"
  }, {
    "product_name" : "Red Hat Enterprise Linux 9",
    "fix_state" : "Not affected",
    "package_name" : "unbound",
    "cpe" : "cpe:/o:redhat:enterprise_linux:9"
  }, {
    "product_name" : "Red Hat OpenShift Container Platform 4",
    "fix_state" : "Not affected",
    "package_name" : "openshift/ose-rhel-coreos-8",
    "cpe" : "cpe:/a:redhat:openshift:4"
  }, {
    "product_name" : "Red Hat OpenShift Container Platform 4",
    "fix_state" : "Affected",
    "package_name" : "openshift/ose-rhel-coreos-9",
    "cpe" : "cpe:/a:redhat:openshift:4"
  } ],
  "references" : [ "https://www.cve.org/CVERecord?id=CVE-2026-32665\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-32665" ],
  "name" : "CVE-2026-32665",
  "mitigation" : {
    "value" : "To mitigate this issue, disable DNS-over-QUIC (DoQ) in the Unbound configuration if it is not a required service. This can typically be achieved by commenting out or removing DoQ-related configuration options in `unbound.conf`. For example, remove or comment out lines such as `do-quic: yes` or `quic-port: 853`.\nAfter modifying the configuration, restart the Unbound service for the changes to take effect:\n```bash\nsystemctl restart unbound\n```\nWarning: Restarting the Unbound service will temporarily interrupt DNS resolution.",
    "lang" : "en:us"
  },
  "csaw" : false
}