Integer Overflow or Wraparound 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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- published31 Jul 2026
- disclosed22 Jul 2026
- creditUnknown
Introduced: 22 Jul 2026
CVE-2026-55991 (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 Integer Overflow or Wraparound via a specially crafted DNS-over-QUIC connection and a single DNS query. An attacker can terminate the process by sending malicious network traffic, resulting in the DNS resolver becoming unavailable. This is only exploitable if DNS-over-QUIC (DoQ) support is enabled in the configuration.
Workaround
This vulnerability can be mitigated by disabling DNS-over-QUIC (DoQ) functionality within the configuration and restarting the service.