A BIND resolver encountering an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode records may fail to properly deallocate internal resources. If this happens repeatedly, resource exhaustion will eventually prevent the resolver from performing new recursive lookups. This issue affects BIND 9 versions 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through 9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1.

The version of ISC BIND running on the remote host is 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, or 9.21.0 through 9.21.25. Supported Preview Edition releases 9.18.11-S1 through 9.18.50-S1 and 9.20.9-S1 through 9.20.27-S1 are also affected. It is, therefore, affected by multiple vulnerabilities :

  - A BIND resolver encountering an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode     records may fail to properly deallocate internal resources. If this happens repeatedly, resource exhaustion     will eventually prevent the resolver from performing new recursive lookups. (CVE-2026-81563)

  - If a BIND resolver has cached a tree of SVCB/HTTPS AliasMode records, and is then queried for the root of     that tree, the resolver will spend disproportionate CPU time constructing the response. (CVE-2026-81736)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

The remote Debian 13 host has packages installed that are affected by multiple vulnerabilities as referenced in the dsa-6505 advisory.

    - -------------------------------------------------------------------------     Debian Security Advisory DSA-6505-1                   security@debian.org     https://www.debian.org/security/                       Moritz Muehlenhoff     September 17, 2026                    https://www.debian.org/security/faq
    - -------------------------------------------------------------------------

    Package        : bind9     CVE ID         : CVE-2026-19033 CVE-2026-19662 CVE-2026-19666 CVE-2026-19667                      CVE-2026-19668 CVE-2026-75029 CVE-2026-76163 CVE-2026-77119                      CVE-2026-77692 CVE-2026-80274 CVE-2026-81563 CVE-2026-81736

    Several vulnerabilities were discovered in BIND, a DNS server implementation,     which may result in denial of service or cache poisoning.

    For the stable distribution (trixie), these problems have been fixed in     version 1:9.20.29-1~deb13u1.

    We recommend that you upgrade your bind9 packages.

    For the detailed security status of bind9 please refer to     its security tracker page at:
    https://security-tracker.debian.org/tracker/bind9

    Further information about Debian Security Advisories, how to apply     these updates to your system and frequently asked questions can be     found at: https://www.debian.org/security/

    Mailing list: debian-security-announce@lists.debian.org

Tenable has extracted the preceding description block directly from the Debian security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - A BIND resolver encountering an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode     records may fail to properly deallocate internal resources. If this happens repeatedly, resource     exhaustion will eventually prevent the resolver from performing new recursive lookups. This issue affects     BIND 9 versions 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, 9.18.11-S1 through     9.18.50-S1, and 9.20.9-S1 through 9.20.27-S1. (CVE-2026-81563)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Type	Severity
347971	ISC BIND 9.18.0 < 9.20.29 / 9.18.11-S1 < 9.20.29-S1 / 9.20.0 < 9.20.29 / 9.20.9-S1 < 9.20.29-S1 / 9.21.0 < 9.21.26 Multiple Vulnerabilities	Nessus	DNS	Remote	high
346980	Debian dsa-6505 : bind9 - security update	Nessus	Debian Local Security Checks	Local	medium
346645	Linux Distros Unpatched Vulnerability : CVE-2026-81563	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2026-81563

high

Tenable Plugins

high

medium

high