SB2025082803 - Debian update for unbound

CSH
CYBERSECURITY HELP
Sign In REGISTER

Main Vulnerability Database SB2025082803

SB2025082803 - Debian update for unbound

Published: August 28, 2025

Security Bulletin ID SB2025082803
Severity
Medium
Patch available
YES
Number of vulnerabilities 3
Exploitation vector Remote access
Highest impact Denial of service

Breakdown by Severity

Medium 100%
  • Low
  • Medium
  • High
  • Critical

Description

This security bulletin contains information about 3 secuirty vulnerabilities.


1) Resource exhaustion (CVE-ID: CVE-2024-8508)

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to application does not properly control consumption of internal resources when handling replies with very large RRsets. A remote attacker can trigger resource exhaustion and perform a denial of service (DoS) attack.


2) Resource management error (CVE-ID: CVE-2024-33655)

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to way Unbound queues DNS requests, which makes it susceptible to DNSBomb attack. A remote attacker with ability to control the delay of the malicious authoritative answers can force Unbound to slowly accumulate pending answers for the spoofed addresses. When the authoritative answers become available to Unbound at the same time, Unbound starts serving all the accumulated queries. This results in large-sized, concentrated response bursts to the spoofed addresses.

Unbound itself is not vulnerable for DoS, rather it can be used to take part in a pulsing DoS amplification attack.


3) Acceptance of Extraneous Untrusted Data With Trusted Data (CVE-ID: CVE-2025-5994)

The vulnerability allows a remote attacker to perform cache poisoning attacks.

The vulnerability exists due to a logic error in the EDNS Client Subnet (ECS) implementation. A remote attacker can perform cache poisoning attacks against Unbound servers with ECS support, a.k.a. Rebirthday Attack.

Successful exploitation of the vulnerability requires that the server is compiled with '--enable-subnet' and configured to send ECS information to upstream name servers with at least one of the 'send-client-subnet', 'client-subnet-zone' or 'client-subnet-always-forward' options.


Remediation

Install update from vendor's website.

References