CVE detail
CVE-2026-44687
In NLnet Labs Unbound 1.13.2 up to and including 1.25.1, stub or forward zones where the name is below an intermediate labed below a DNSSEC signed zone could be shadowed by the intermediate label's secure NXDOMAIN answer from the parent. This is caused by an off-by-one error in 'harden-below-nxdomain' logic; enabled by default. It effectively bypasses the configuration and the configured stub/forward zone is never contacted. 'harden-below-nxdomain' does an upward DNS cache walk together with a delegation point guard that does not allow NXDOMAIN synthesis above stub/forward zones. The guard tests the domain name but before stripping a label. This results in an iteration where the domain name equals the configured stub/forward zone apex that passes the guard, strips one more label, and probes the cache at the apex's immediate public parent. If that parent has a cached DNSSEC-secure NXDOMAIN, which it will for any private namespace nested two or more labels under a signed public name, the walk returns it and the configured stub/forward upstream is never contacted. This can only be triggered by the query for the intermediate label (between the stub/forward apex and the DNSSEC parent zone).
Buzz score
Why this CVE is surfacing
This all-time snapshot uses the same composite formula as Trending across a 30-year evidence window, rather than a current rolling window.
Buzz score components · mention 11.0 · diversity 10.0 · KEV 0.0 · OTX 0.0 · PoC 0.0
Why it matters now
Mention timeline
- Total mentions
- 2
- within the 30d window
- Peak daily
- 1
- highest bucket
Evidence
Source links by recency
2 source links · newest first
Information published.
vendormsrc.microsoft.comJul 23, 2026, 8:03 AM- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44687.txtwww.nlnetlabs.nl
No excerpt available.
Vendor Advisorywww.nlnetlabs.nlJul 22, 2026, 2:17 PM
Exploit code
Public exploit repository references
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0 repository references · best confidence N/A · max 0 stars
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