Preparing an NSEC3 closest encloser proof can exhaust CPU resources
CVE: CVE-2023-50868
Component: bind9
CWE: CWE-400
Severity: Important
CVSS v3: 7.5/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Release date: 2023-01-01T00:00:00+00:00

A flaw was found in bind9. By flooding a DNSSEC resolver with responses coming from a DNSEC-signed zone using NSEC3, an attacker can lead the targeted resolver to a CPU exhaustion, further leading to a Denial of Service on the targeted host.

This vulnerability applies only for systems where DNSSEC validation is enabled.

Statement: The vulnerability in BIND9 that leads to CPU exhaustion through a flood of DNSSEC responses with NSEC3 signatures is a important severity issue due to its potential to induce a Denial of Service (DoS) condition on affected resolvers. By exploiting this flaw, an attacker can overwhelm a DNSSEC-enabled resolver with computationally intensive tasks, depleting CPU resources and disrupting normal DNS operations. This can result in significant service outages, affecting the resolver's ability to process legitimate DNS queries and thereby compromising network availability and reliability. The impact is exacerbated in high-traffic environments or where DNSSEC validation is extensively employed, making prompt remediation essential to prevent operational disruptions and maintain DNS infrastructure integrity.

Remediation:
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
Before applying this update, make sure all previously released errata
relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

After installing the update, the BIND daemon (named) will be restarted automatically.
Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258
Before applying this update, make sure all previously released errata relevant to your system have been applied.

For details on how to apply this update, refer to:

https://access.redhat.com/articles/11258
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.