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VulnerabilityPublished Updated

CVE-2026-81563: ISC BIND 9 · Memory Leak

Affects ISC BIND 9Source CVE Database V5

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Not known to be exploited · CVSS 7.5 High.

Data as of 31 Oct 2026, 08:20 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 16 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
ISCBIND 9Affected
  • >=9.18.0 <=9.18.50
  • >=9.20.0 <=9.20.27
  • >=9.21.0 <=9.21.25
  • >=9.18.11-S1 <=9.18.50-S1
  • >=9.20.9-S1 <=9.20.27-S1
Fixed in–
Iscisc/bind9pkg:deb/isc/bind9Other threatsAffected
  • >=9.18.0 <=9.18.50
  • >=9.20.0 <=9.20.27
  • >=9.21.0 <=9.21.25
  • >=9.18.11-S1 <=9.18.50-S1
  • >=9.20.9-S1 <=9.20.27-S1
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until an official fix is available, monitor resource usage on BIND 9 resolvers and consider limiting exposure to crafted SVCB/HTTPS records if possible.

Description

CVE-2026-81563 is a high-severity memory management vulnerability in ISC BIND 9. It occurs when a BIND resolver processes an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode records, leading to failure in releasing internal resources. This can cause resource exhaustion and prevent new recursive DNS lookups. The vulnerability affects multiple BIND 9 versions from 9.18.0 through 9.18.50, 9.20.0 through 9.20.27, 9.21.0 through 9.21.25, and several S1 variants. No patch or remediation details are provided, and no known exploits are reported in the wild.

References

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