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F5 Networks BIG-IP : NLnet Labs Unbound vulnerability (K000162877)
medium Nessus Plugin ID 334950
Synopsis
The remote device is missing a vendor-supplied security patch.Description
The version of F5 Networks BIG-IP installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the K000162877 advisory.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.(CVE-2026-44390)
Tenable has extracted the preceding description block directly from the F5 Networks BIG-IP security advisory.
Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.
Solution
The vendor has acknowledged the vulnerability, but no solution has been provided.Refer to the vendor for remediation guidance.
See Also
Plugin Details
Severity: Medium
ID: 334950
File Name: f5_bigip_SOL000162877.nasl
Version: 1.1
Type: Local
Published: 8/12/2026
Updated: 8/12/2026
Configuration: Enable paranoid mode
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: Low
Score: 1.2
Percentile: 0.01
CVSS v2
Risk Factor: Medium
Base Score: 5
Temporal Score: 3.7
Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P
CVSS Score Source: CVE-2026-44390
CVSS v3
Risk Factor: Medium
Base Score: 5.3
Temporal Score: 4.6
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C
CVSS v4
Risk Factor: Medium
Base Score: 6.9
Threat Score: 2.7
Threat Vector: CVSS:4.0/E:U
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
Vulnerability Information
CPE: cpe:/a:f5:big-ip_domain_name_system, cpe:/a:f5:big-ip_global_traffic_manager, cpe:/h:f5:big-ip
Required KB Items: Host/local_checks_enabled, Settings/ParanoidReport, Host/BIG-IP/hotfix, Host/BIG-IP/modules, Host/BIG-IP/version
Exploit Ease: No known exploits are available
Vulnerability Publication Date: 5/20/2026
Reference Information
CVE: CVE-2026-44390