What’s Vulnerable › Vulnerabilities

CVE-2026-81563: SVCB AliasMode additional-data error leaks qpcache references

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.6% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-16 · updated 2026-10-26
• Weakness: CWE-401

Description

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.

Affected products

• ISC BIND: from 9.18.0 through 9.18.50; from 9.20.0 through 9.20.27; from 9.21.0 through 9.21.25; from 9.18.11-S1 through 9.18.50-S1; from 9.20.9-S1 through 9.20.27-S1

References

• https://downloads.isc.org/isc/bind9/9.20.29
• https://downloads.isc.org/isc/bind9/9.21.26
• https://kb.isc.org/docs/cve-2026-81563

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