CVE-2026-32665
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U
Exploit Intelligence
Low risk: more likely to be exploited than 21% of all known CVEs.
References
Related Vulnerabilities
Other CWE-1284 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2022-20699 | Critical | 10.0 | 72% | KEV | - |
| CVE-2021-43267 | Critical | 9.8 | 58% | - | Fix |
| CVE-2022-31629 | Medium | 6.5 | 49% | - | Fix |
| CVE-2025-9316 | Unscored | - | 36% | - | - |
| CVE-2022-36620 | High | 7.5 | 23% | - | - |
| CVE-2008-1440 | High | 7.1 | 23% | - | - |
Common questions
How do I fix CVE-2026-32665?
Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-32665 being actively exploited?
Not that we know of. CVE-2026-32665 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.29% is the estimated probability that it will be exploited in the next 30 days. That is higher than 21% of all scored CVEs.
How severe is CVE-2026-32665?
CVE-2026-32665 has a CVSS v3 base score of 7.5, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-32665 affect?
Published advisories record a fix for unbound (Debian), unbound (Rocky), unbound (Red Hat / RHEL). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-24.