Improper Update of Reference Count Affecting unbound package, versions [1.22.0,1.25.2)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-UNMANAGED-UNBOUND-18507934
- published2 Aug 2026
- disclosed22 Jul 2026
- creditUnknown
Introduced: 22 Jul 2026
NewCVE-2026-41637 (opens in a new tab)How to fix?
Upgrade unbound to version 1.25.2 or higher.
Overview
Affected versions of this package are vulnerable to Improper Update of Reference Count in the handling of terminated DNS-over-QUIC queries. An attacker can cause resource exhaustion by sending and immediately terminating multiple DNS-over-QUIC queries from different source IPs, leading to a build-up of pending responses and service degradation for new clients. This is only exploitable if the software is explicitly compiled with --with-libngtcp2 and the quic-port is configured, and if the attacker can bypass default rate limits using multiple source IPs.
Workaround
This vulnerability can be mitigated by disabling DNS-over-QUIC (DoQ) support by removing or commenting out the quic-port directive in the configuration and restarting the service.