CVE-2026-56444 Detail
Received
This CVE record has recently been published to the CVE List and has been included within the NVD dataset. DescriptionIn NLnet Labs Unbound 1.20.0 up to and including 1.25.1, when Unbound is configured with 'serve-expired: yes' and 'serve-expired-client-timeout > discard-timeout > 0' (contrary to the suggested values), the discard-timeout branch during the serve expired logic drops an aged client reply without performing the correct accounting for the number of reply addresses for the query. Other identical branches outside of serve expired perform the correct decrement. Since the counter is never decremented in such scenario, it can reach the maximum limit and new clients for duplicate in-flight queries are silently dropped resulting in degradation of resolution service. A malicious actor can exploit the vulnerability by querying the resolver for a client-controlled slow-on-demand authoritative zone that can drive the counter past the threshold. Shipped defaults for 'serve-expired-client-timeout: 1800' and 'discard-timeout: 1900' make the branch unreachable. Metrics
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CVSS 4.0 Severity and Vector Strings:
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Weakness Enumeration
Quick InfoCVE Dictionary Entry:CVE-2026-56444 NVD Published Date: 07/22/2026 NVD Last Modified: 07/22/2026 Source: NLnet Labs |
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