Resource exhaustion in Unbound - CVE-2026-44390
Published: May 20, 2026
Vulnerability identifier: #VU131932
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-44390
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: NLnet Labs
Affected software:
Unbound
Unbound
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in name compression handling for downstream replies when processing malicious upstream responses with very large RRsets whose records do not share a suffix above the root. A remote attacker can query Unbound for specially crafted contents of a malicious zone to cause a denial of service.
The issue can lock the CPU while the reply packet is being completed, leading to degraded performance before service disruption.
How to mitigate CVE-2026-44390
Install security update from vendor's website.