What is CVE-2026-81563?

CVE-2026-81563 is a high-severity vulnerability in Isc Bind 9, classified under Missing Release of Memory after Effective Lifetime. CVSS score: 7.5/10. Published 2026-09-16.

How severe is CVE-2026-81563?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Isc Bind 9

CVE-2026-81563

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.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Affected products

Isc Bind 9

Weakness classification (CWE)

CWE-401 — Missing Release of Memory after Effective Lifetime

References

security-officer@isc.org (patch)
security-officer@isc.org (patch)
security-officer@isc.org (vendor-advisory)

Frequently asked questions

What is CVE-2026-81563?: CVE-2026-81563 is a high-severity vulnerability in Isc Bind 9, classified under Missing Release of Memory after Effective Lifetime. CVSS score: 7.5/10. Published 2026-09-16.
How severe is CVE-2026-81563?: High severity. CVSS v3 base score is 7.5 out of 10.