Detections
Analytics

Echo: unbound: security update to 1.25.2

medium Tenable Cloud Security Plugin ID 461698

Description

There are packages installed that are affected by a vulnerability referenced in the following CVE:

 - In NLnet Labs Unbound 1.10.0 up to and including 1.25.1, when 'serve-expired: yes' is set together with a
 'response-ip: <net> redirect' /'response-ip-data: <net> CNAME <target>' rule (or the RPZ 'rpz-cname-
 override' equivalent), a remote client who controls any delegated domain can crash the daemon. The serve-
 expired-client-timeout callback runs a two-pass loop to chase the respip-generated CNAME alias; on the
 second pass it resets 'alias_rrset' but not 'partial_rep'. Later, this inconsistency leads to a NULL
 pointer dereference and an eventual crash. A malicious actor can exploit the vulnerability by controlling
 any zone that replies with an A/AAAA record that falls inside the configured response-ip/rpz subnet. By
 delaying the answer when the previous record has expired, the vulnerable path of 'serve-expired-client-
 timeout' is taken leading to denial of service via the server crash. (CVE-2026-55717)

Solution

Update the unbound library and its related packages to version 1.25.2 or later.

See Also

https://advisory.echohq.com/cve/CVE-2026-55717

Plugin Details

Severity: Medium

ID: 461698

Version: Revision 1.1

Type: Local

Published: 10/2/2026

Updated: 10/2/2026

Risk Information

VPR

Risk Factor: Medium

Score: 5

Percentile: 93.18

CVSS v2

Risk Factor: Medium

Base Score: 5.4

Temporal Score: 4

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

CVSS Score Source: CVE-2026-55717

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.2

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

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

Vulnerability Information

Exploit Ease: No known exploits are available

Patch Publication Date: 7/23/2026

Vulnerability Publication Date: 7/22/2026

Reference Information

CVE: CVE-2026-55717