CVE-2026-81736 PUBLISHED

Remote CPU denial of service through cached SVCB/HTTPS AliasMode trees

Assigner: isc
Reserved: 27.08.2026 Published: 16.09.2026 Updated: 16.09.2026

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. 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.

Metrics

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS Score: 7.5

Product Status

Vendor ISC
Product BIND 9
Versions Default: unaffected
  • affected from 9.18.0 to 9.18.50 (incl.)
  • affected from 9.20.0 to 9.20.27 (incl.)
  • affected from 9.21.0 to 9.21.25 (incl.)
  • affected from 9.18.11-S1 to 9.18.50-S1 (incl.)
  • affected from 9.20.9-S1 to 9.20.27-S1 (incl.)

Exploits

We are not aware of any active exploits.

Workarounds

No workarounds known.

Solutions

Upgrade to the patched release most closely related to your current version of BIND 9: 9.20.29, 9.21.26, or 9.20.29-S1.

Credits

  • ISC would like to thank Henrique Pereira for bringing this vulnerability to our attention.

References

Problem Types

  • CWE-1050 Excessive Platform Resource Consumption within a Loop CWE

Impacts

  • A successful attack may result in resource exhaustion and a denial-of-service.