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VulnerabilityPublished Updated

CVE-2026-5946: ISC BIND 9 · Improper Input Validation

Affects ISC BIND 9Source CVE Database V5

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Not known to be exploited · CVSS 7.5 High · fixed in 9.21.22 : patch ISC BIND 9 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
1.9% chance of exploitation in 30 days – higher than 80% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 9.21.22, 9.20.23, 9.18.49 +1
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 20 May 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

Upgrade isc/bind9 to 9.21.22, 9.20.23, 9.18.49 or 9.16.51.

Affected software

ProductAffectedFixed in
ISCBIND 9Affected
  • >=9.11.0 <=9.16.50
  • >=9.18.0 <=9.18.48
  • >=9.20.0 <=9.20.22
  • >=9.21.0 <=9.21.21
  • >=9.11.3-S1 <=9.16.50-S1
  • >=9.18.11-S1 <=9.18.48-S1
  • >=9.20.9-S1 <=9.20.22-S1
Fixed in–
Iscisc/bind9pkg:deb/isc/bind9Other threatsAffected
  • 9.11.0 – 9.21.0
  • 9.11.0 <9.16.51
  • 9.18.0 <9.18.49
  • 9.20.0 <9.20.23
  • 9.21.0 <9.21.22
7 affected builds
Fixed in
  • 9.16.51
  • 9.18.49
  • 9.20.23
  • 9.21.22

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

AI-suggested

A patch is available and has been released by ISC and vendors such as Red Hat. Users should apply the official security updates to affected BIND 9 versions as soon as possible. Vendor advisories indicate that no effective mitigations other than patching currently meet criteria for ease of use and applicability. Red Hat customers should follow the update instructions in their advisories. Monitoring for unusual DNS message classes and restricting access to DNS services may reduce exposure but are not formal mitigations.

Description

Multiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) — for example, `CHAOS` or `HESIOD`, or DNS messages that specify meta-classes (`ANY` or `NONE`) in the question section. Specially crafted requests reaching the affected code paths — recursion, dynamic updates (`UPDATE`), zone change notifications (`NOTIFY`), or processing of `IN`-specific record types in non-`IN` data — can cause assertion failures in `named`. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

References

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