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.
Advisories
No advisories yet.
Fixes
Solution
This issue is fixed starting with version 1.25.2
Workaround
No workaround given by the vendor.
References
History
Mon, 27 Jul 2026 20:30:00 +0000
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Nlnetlabs
Nlnetlabs unbound |
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Nlnetlabs
Nlnetlabs unbound |
Wed, 22 Jul 2026 15:30:00 +0000
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ssvc
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Wed, 22 Jul 2026 13:30:00 +0000
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| Description | 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. | |
| Title | Degradation of resolution service from improperly accounted client-terminated DNS-over-QUIC queries | |
| Weaknesses | CWE-772 | |
| References |
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| Metrics |
cvssV3_1
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Projects
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Status: PUBLISHED
Assigner: NLnet Labs
Published:
Updated: 2026-07-22T14:29:25.088Z
Reserved: 2026-06-22T10:11:10.518Z
Link: CVE-2026-41637
Updated: 2026-07-22T14:29:17.367Z
No data.
No data.
OpenCVE Enrichment
Updated: 2026-07-27T20:15:03Z
Weaknesses