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F5 Networks BIG-IP : NLnet Labs Unbound vulnerability (K000163139)
critical Nessus Plugin ID 341737
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 K000163139 advisory.NLnet Labs Unbound 1.19.1 up to and including version 1.25.0 has a vulnerability in the DNSSEC validator that enables denial of service and possible remote code execution as a result of deep copying a data structure and erroneously overwriting a destination pointer. An adversary can exploit the vulnerability by controlling a malicious signed zone and querying a vulnerable Unbound. When DS sub-queries need to suspend validation due to NSEC3 computational budget exhaustion (introduced in Unbound 1.19.1), Unbound deep- copies response messages to preserve them across memory region teardown. A struct-assignment bug overwrites the destination's pointer with the source's pointer. After the sub-query region is freed, the resumed validator dereferences this dangling pointer, triggering a crash or potentially enabling arbitrary code execution. Unbound 1.25.1 contains a patch with a fix to preserve the correct pointer when deep copying the data structure.(CVE-2026-33278)
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: Critical
ID: 341737
File Name: f5_bigip_SOL000163139.nasl
Version: 1.1
Type: Local
Published: 8/31/2026
Updated: 8/31/2026
Configuration: Enable paranoid mode
Supported Sensors: Nessus
Risk Information
VPR
Risk Factor: High
Score: 7.6
Percentile: 98.4
CVSS v2
Risk Factor: Critical
Base Score: 10
Temporal Score: 7.4
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:C
CVSS Score Source: CVE-2026-33278
CVSS v3
Risk Factor: Critical
Base Score: 9.8
Temporal Score: 8.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C
CVSS v4
Risk Factor: Critical
Base Score: 10
Threat Score: 9.1
Threat Vector: CVSS:4.0/E:U
Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H
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, Host/BIG-IP/hotfix, Host/BIG-IP/modules, Host/BIG-IP/version, Settings/ParanoidReport
Exploit Ease: No known exploits are available
Vulnerability Publication Date: 5/20/2026
Reference Information
CVE: CVE-2026-33278