CVE-2026-81563Network attack vector

Recursive DNS denial of service via qpcache leak

Published Sep 16, 2026 · Updated Sep 16, 2026

Resource exhaustion in BIND 9 affected branches allows remote attackers to stop recursive DNS lookups via crafted SVCB/HTTPS records. The resolver's AliasMode additional-data error path fails to release qpcache references when one alias points to at least 14 ServiceMode records. Repeated processing consumes memory beyond configured limits until named is terminated or can no longer perform new recursive lookups.

CVSS severity7.5
High
EPSS probabilityUnavailable
No score available in this record
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in BIND 9 affected branches allows remote attackers to stop recursive DNS lookups via crafted SVCB/HTTPS records. The resolver's AliasMode additional-data error path fails to release qpcache references when one alias points to at least 14 ServiceMode records. Repeated processing consumes memory beyond configured limits until named is terminated or can no longer perform new recursive lookups.

The record

CVE
CVE-2026-81563
Published
Sep 16, 2026
Updated
Sep 16, 2026
Vendor
Internet Systems Consortium
Product
BIND 9
Classifications
T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 16, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=9.18.0 <=9.18.50
  2. Affected versionversion=9.18.11-S1 <=9.18.50-S1
  3. Affected versionversion=9.20.0 <=9.20.27
  4. Affected versionversion=9.20.9-S1 <=9.20.27-S1
  5. Affected versionversion=9.21.0 <=9.21.25

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Internet Systems Consortium · BIND 9version=9.18.0 <=9.18.50; version=9.18.11-S1 <=9.18.50-S1; version=9.20.0 <=9.20.27; version=9.20.9-S1 <=9.20.27-S1; version=9.21.0 <=9.21.25

Published CVSS scores

7.5Internet Systems ConsortiumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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