CVE-2026-44390
published 2026-05-20CVE-2026-44390: 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…
PriorityP432medium5.3CVSS 3.1
AVNACLPRNUINSUCNINAL
EPSS
0.56%
42.2th percentile
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.
Affected
3 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| nlnetlabs | unbound | < 1.25.1 | 1.25.1 |
| nlnetlabs | unbound | — | — |
| ubuntu | unbound | — | — |
CVSS provenance
nvdv3.15.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
nvdv4.06.9MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
vendor_redhat5.3MEDIUM
vendor_ubuntu4.6MEDIUM
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BSD
FreeBSD-SA-26:33.unbound: Multiple vulnerabilities in unbound
bsd_advisories·2026-06-09·CVSS 5.3
CVE-2026-32792 [MEDIUM] FreeBSD-SA-26:33.unbound: Multiple vulnerabilities in unbound
FreeBSD-SA-26:33.unbound Security Advisory
The FreeBSD Project
Topic: Multiple vulnerabilities in unbound
Category: contrib
Module: unbound
Announced: 2026-06-09
Affects: All supported versions of FreeBSD
Corrected: 2026-05-26 16:48:51 UTC (stable/15, 15.1-STABLE)
2026-05-28 22:16:07 UTC (releng/15.1, 15.1-RC2)
2026-06-09 19:19:52 UTC (releng/15.0, 15.0-RELEASE-p10)
2026-05-26 16:49:56 UTC (stable/14, 14.4-STABLE)
2026-06-09 19:19:14 UTC (releng/14.4, 14.4-RELEASE-p6)
2026-06-09 19:18:44 UTC (releng/14.3, 14.3-RELEASE-p15)
CVE Name: CVE-2026-32792, CVE-2026-33278, CVE-2026-40622,
CVE-2026-41292, CVE-2026-42534, CVE-2026-42923,
CVE-2026-42944, CVE-2026-42959, CVE-2026-42960,
CVE-2026-44390, CVE-2026-44608
For general information regarding FreeBSD Security Advisories,
including descriptio
Ubuntu
Unbound vulnerabilities
vendor_ubuntu·2026-06-02·CVSS 4.6
CVE-2026-42959 [MEDIUM] Unbound vulnerabilities
Title: Unbound vulnerabilities
Summary: Several security issues were fixed in Unbound.
USN-8282-1 fixed vulnerabilities in Unbound. This update provides the
corresponding updates for CVE-2026-41292 in Ubuntu 18.04 LTS and Ubuntu
20.04 LTS and CVE-2026-42959, CVE-2026-42960 in Ubuntu 14.04 LTS, Ubuntu
16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS.
Original advisory details:
Andrew Griffiths discovered that Unbound did not properly handle certain
DNSCrypt packets. A remote attacker could possibly use this issue to cause
Unbound to crash, resulting in a denial of service. (CVE-2026-32792)
Qifan Zhang discovered that Unbound incorrectly handled DNSSEC validation
in certain situations. A remote attacker could possibly use this issue to
execute arbitrary code. This issue only affected U
Red Hat
unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets
vendor_redhat·2026-05-20·CVSS 5.3
CVE-2026-44390 [MEDIUM] CWE-1050 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets
unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets
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
Ubuntu
Unbound vulnerabilities
vendor_ubuntu·2026-05-20·CVSS 4.6
CVE-2026-33278 [MEDIUM] Unbound vulnerabilities
Title: Unbound vulnerabilities
Summary: Several security issues were fixed in Unbound.
Andrew Griffiths discovered that Unbound did not properly handle certain
DNSCrypt packets. A remote attacker could possibly use this issue to cause
Unbound to crash, resulting in a denial of service. (CVE-2026-32792)
Qifan Zhang discovered that Unbound incorrectly handled DNSSEC validation
in certain situations. A remote attacker could possibly use this issue to
execute arbitrary code. This issue only affected Ubuntu 24.04 LTS,
Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-33278)
Qifan Zhang discovered that Unbound incorrectly handled certain ghost
domain name records. A remote attacker could possibly use this issue to
cause a denial of service. This issue only affected Ubuntu 24.04 LTS,
Ubuntu 25.10
VulDB
NLnet Labs Unbound up to 1.25.0 algorithmic complexity (Nessus ID 315778 / WID-SEC-2026-1599)
vuldb·2026-05-26·CVSS 6.9
CVE-2026-44390 [MEDIUM] NLnet Labs Unbound up to 1.25.0 algorithmic complexity (Nessus ID 315778 / WID-SEC-2026-1599)
A vulnerability was found in NLnet Labs Unbound up to 1.25.0 and classified as problematic. The impacted element is an unknown function. Such manipulation leads to inefficient algorithmic complexity.
This vulnerability is traded as CVE-2026-44390. The attack may be launched remotely. There is no exploit available.
It is suggested to upgrade the affected component.
GHSA
GHSA-6522-r5fq-99gw: NLnet Labs Unbound up to and including version 1
ghsa_unreviewed·2026-05-20·CVSS 5.3
CVE-2026-44390 [MEDIUM] CWE-407 GHSA-6522-r5fq-99gw: NLnet Labs Unbound up to and including version 1
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 li
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-44390 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets [fedora-all]
bugzilla·2026-06-22·CVSS 5.3
CVE-2026-44390 [MEDIUM] CVE-2026-44390 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets [fedora-all]
CVE-2026-44390 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Bugzilla
CVE-2026-44390 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets
bugzilla·2026-05-20·CVSS 5.3
CVE-2026-44390 [MEDIUM] CVE-2026-44390 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets
CVE-2026-44390 unbound: Unbound: Denial of Service due to excessive resource consumption with large DNS Resource Record Sets
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 n
2026-05-20
Published