CVE-2026-41637
LOW 3.7 ALL-YEARSIn 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.
No known exploitation, public exploit, or elevated probability at this time. Track for changes.
Exploitation likelihood
0.4%chance of exploitation in 30 days · 30th percentile
Impact if exploited
3.7CVSS 3.1 · LOW · CNA
- ConfidentialityNone
- IntegrityNone
- AvailabilityLow
What an attacker needs
- ✓Access: Reachable over the network — no local access needed
- ✓Privileges: No account or privileges required
- ✓User interaction: No user interaction needed
- ⚠Complexity: Needs a race window or specific setup
✓ lowers the bar for an attacker · ⚠ raises it
Proof of concept
No public PoC is currently catalogued.
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Tracked sources are checked weekly for the full archive, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.
Weakness (CWE)
- CWE-772: : Missing Release of Resource after Effective Lifetime
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
References and research data (JSON)
Vendor product assessments
Showing 32 of 35 vendor product statements; 3 omitted. Read the full vendor advisory.
unbound-main@aarch64 as a component of Red Hat Hardened Images · fixed
Vendor assessment for this product only.
pkg:rpm/redhat/[email protected]?arch=aarch64&distro=hummingbird-20251124&repository_id=public-hummingbird-aarch64-rpms
- vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
unbound-main@noarch as a component of Red Hat Hardened Images · fixed
Vendor assessment for this product only.
pkg:rpm/redhat/[email protected]?arch=noarch&distro=hummingbird-20251124&repository_id=public-hummingbird-x86_64-rpms
- vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
unbound-main@src as a component of Red Hat Hardened Images · fixed
Vendor assessment for this product only.
pkg:rpm/redhat/[email protected]?arch=src&distro=hummingbird-20251124&repository_id=public-hummingbird-source-rpms
- vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
unbound-main@x86_64 as a component of Red Hat Hardened Images · fixed
Vendor assessment for this product only.
pkg:rpm/redhat/[email protected]?arch=x86_64&distro=hummingbird-20251124&repository_id=public-hummingbird-x86_64-rpms
- vendor fix: For details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/ Vendor guidance
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
python3-unbound as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/python3-unbound
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound-anchor as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound-anchor
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound-devel as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound-devel
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound-libs as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound-libs
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound-utils as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound-utils
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound.src as a component of Red Hat Enterprise Linux 10 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound?arch=src
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
python3-unbound as a component of Red Hat Enterprise Linux 9 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/python3-unbound
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound as a component of Red Hat Enterprise Linux 9 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound-devel as a component of Red Hat Enterprise Linux 9 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound-devel
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound-libs as a component of Red Hat Enterprise Linux 9 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound-libs
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound.src as a component of Red Hat Enterprise Linux 9 · known affected
Vendor assessment for this product only.
pkg:rpm/redhat/unbound?arch=src
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
openshift/ose-rhel-coreos-8 as a component of Red Hat OpenShift Container Platform 4 · known affected
Vendor assessment for this product only.
pkg:oci/ose-rhel-coreos-8?repository_url=registry.redhat.io/openshift/ose-rhel-coreos-8
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
openshift/ose-rhel-coreos-9 as a component of Red Hat OpenShift Container Platform 4 · known affected
Vendor assessment for this product only.
pkg:oci/ose-rhel-coreos-9?repository_url=registry.redhat.io/openshift/ose-rhel-coreos-9
- workaround: To mitigate this issue, completely disable DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in your Unbound configuration. Restart the Unbound service to apply the changes and clear any lingering resource limits.
- none available: Fix deferred
unbound as a component of Red Hat Enterprise Linux 6 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-devel as a component of Red Hat Enterprise Linux 6 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-devel
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-libs as a component of Red Hat Enterprise Linux 6 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-libs
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-python as a component of Red Hat Enterprise Linux 6 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-python
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound.src as a component of Red Hat Enterprise Linux 6 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound?arch=src
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound as a component of Red Hat Enterprise Linux 7 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-devel as a component of Red Hat Enterprise Linux 7 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-devel
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-python as a component of Red Hat Enterprise Linux 7 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-python
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound.src as a component of Red Hat Enterprise Linux 7 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound?arch=src
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00python3-unbound as a component of Red Hat Enterprise Linux 8 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/python3-unbound
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound as a component of Red Hat Enterprise Linux 8 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-devel as a component of Red Hat Enterprise Linux 8 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-devel
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound-libs as a component of Red Hat Enterprise Linux 8 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound-libs
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00unbound.src as a component of Red Hat Enterprise Linux 8 · known not affected
Vendor assessment for this product only.
Reason: vulnerable code not present
pkg:rpm/redhat/unbound?arch=src
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
Known Affected Software Configurations
| Vendor | Product | Version range |
|---|---|---|
| Nlnetlabs | Unbound | ≥ 1.22.0 and < 1.25.2 |
All CVSS metrics
- LOW 3.7 v3.1 · CNA Primary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - LOW 3.7 v3.1 · NVD Secondary
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
References
Advisories
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-41637.txt CVE record · NLnet Labs · Updated 2026-07-22T13:04:52.605Z
NVD · CVE-2026-41637 · Updated 2026-10-24T13:10:00.147
Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00 - https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-41637.json Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-47665 EUVD · EUVD-2026-47665
Technical & other
- https://access.redhat.com/security/cve/CVE-2026-41637 Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
- https://bugzilla.redhat.com/show_bug.cgi?id=2506143 Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
- https://www.cve.org/CVERecord?id=CVE-2026-41637 Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
- https://nvd.nist.gov/vuln/detail/CVE-2026-41637 Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
- https://access.redhat.com/errata/RHSA-2026:43588 Red Hat · CVE-2026-41637 · Updated 2026-09-01T12:58:54+00:00
Sources: NVD · CVE.org · All sources and attribution · EPSS