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Amazon Linux 2 : unbound (ALASUNBOUND-1.17-2025-005)

high Nessus Plugin ID 243422

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Synopsis

The remote Amazon Linux 2 host is missing a security update.

Description

The version of unbound installed on the remote host is prior to 1.17.0-2. It is, therefore, affected by a vulnerability as referenced in the ALAS2UNBOUND-1.17-2025-005 advisory.

 A multi-vendor cache poisoning vulnerability named 'Rebirthday Attack' has been discovered in caching resolvers that support EDNS Client Subnet (ECS). Unbound is also vulnerable when compiled with ECS support, i.e., '--enable-subnet', AND configured to send ECS information along with queries to upstream name servers, i.e., at least one of the 'send-client-subnet', 'client-subnet-zone' or 'client-subnet- always-forward' options is used. Resolvers supporting ECS need to segregate outgoing queries to accommodate for different outgoing ECS information. This re-opens up resolvers to a birthday paradox attack (Rebirthday Attack) that tries to match the DNS transaction ID in order to cache non-ECS poisonous replies. (CVE-2025-5994)

Tenable has extracted the preceding description block directly from the tested product 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

Run 'yum update unbound' to update your system.

See Also

https://alas.aws.amazon.com//AL2/ALAS2UNBOUND-1.17-2025-005.html

https://alas.aws.amazon.com/faqs.html

https://explore.alas.aws.amazon.com/CVE-2025-5994.html

Plugin Details

Severity: High

ID: 243422

File Name: al2_ALASUNBOUND-1_17-2025-005.nasl

Version: 1.1

Type: local

Agent: unix

Published: 8/4/2025

Updated: 8/4/2025

Supported Sensors: Frictionless Assessment AWS, Frictionless Assessment Agent, Nessus Agent, Agentless Assessment, Continuous Assessment, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 5.8

Vector: CVSS2#AV:N/AC:L/Au:N/C:N/I:C/A:N

CVSS Score Source: CVE-2025-5994

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

CVSS v4

Risk Factor: High

Base Score: 8.7

Threat Score: 6.6

Threat Vector: CVSS:4.0/E:U

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Vulnerability Information

CPE: p-cpe:/a:amazon:linux:unbound-anchor, p-cpe:/a:amazon:linux:unbound-devel, p-cpe:/a:amazon:linux:python2-unbound, p-cpe:/a:amazon:linux:unbound-debuginfo, p-cpe:/a:amazon:linux:unbound-libs, cpe:/o:amazon:linux:2, p-cpe:/a:amazon:linux:unbound-utils, p-cpe:/a:amazon:linux:unbound, p-cpe:/a:amazon:linux:python3-unbound

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 7/29/2025

Vulnerability Publication Date: 7/16/2025

Reference Information

CVE: CVE-2025-5994