CVE-2026-44390NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability when handling replies with very large RRsets that Unbound needs to perform name compression for.
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NLnet Labs Unbound up to and including version 1.25.0 has a vulnerability when handling replies with very large RRsets that Unbound needs to perform name compression for. Malicious upstream responses with very large RRsets with records that don't share a suffix above the root can cause Unbound to spend a considerable time applying name compression to downstream replies. This can lead to degraded performance and eventually denial of service in well orchestrated attacks. An adversary can exploit the vulnerability by querying Unbound for the specially crafted contents of a malicious zone with very large RRsets. Before Unbound replies to the query it will try to apply name compression which was an unbounded operation that could lock the CPU until the whole packet was complete. A compression limit was introduced in 1.21.1 for this but it didn't account for the case where records would not share any suffix above the root. That causes Unbound to go in a different code path because of the compression tree lookup failure and eventually not increment the compression counter for those operations. Unbound 1.25.1 contains a patch with a fix that increments the compression counter regardless of the compression tree lookup. This is a complement fix to CVE-2024-8508.
- CVSS
- 5.3 MEDIUM (v3.1, NVD)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Weakness (CWE)
- CWE-407, CWE-1050
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Not given
- NVD analysis
- Modified
- Record last updated
- Sep 1, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
nlnetlabs unbound nlnetlabs:unbound | before 1.25.1 | NVD |
References
- https://www.nlnetlabs.nl/downloads/unbound/CVE-2026-44390.txtmitigation, vendor-advisory
- https://access.redhat.com/errata/RHSA-2026:24013
- https://access.redhat.com/errata/RHSA-2026:36320
- https://access.redhat.com/errata/RHSA-2026:36777
- https://access.redhat.com/errata/RHSA-2026:37282
- https://access.redhat.com/security/cve/CVE-2026-44390
- https://bugzilla.redhat.com/show_bug.cgi?id=2480130
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-44390.json
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.