Bind9: A validly signed NSEC3 from an unrelated sibling zone may be accepted as an insecurity proof, downgrading a
Affects bind9Source GCVE Database
Not known to be exploited · CVSS 5.9 Medium · fixed in 1:9.9.5.dfsg-3ubuntu0.19+esm15 : update bind9 when convenient.
Data as of 3 Nov 2026, 23:36 UTC
- Patch
- Available – fixed in 1:9.9.5.dfsg-3ubuntu0.19+esm15, 1:9.10.3.dfsg.P4-8ubuntu1.19+esm11, 1:9.11.3+dfsg-1ubuntu1.19+esm6 +5
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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 3 Nov 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Patches and advisories
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.10bind9pkg:deb/ubuntu/bind9?arch=source&distro=stonkingOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSbind9pkg:deb/ubuntu/bind9?arch=source&distro=resoluteOther threats | Affected
| Fixed in
|
Ubuntu 26.04 LTSisc-dhcppkg:deb/ubuntu/isc-dhcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 24.04 LTSbind9pkg:deb/ubuntu/bind9?arch=source&distro=nobleOther threats | Affected
| Fixed in
|
Ubuntu 24.04 LTSisc-dhcppkg:deb/ubuntu/isc-dhcp?arch=source&distro=nobleOther threats | Affected
| Fixed in– |
Ubuntu 22.04 LTSbind9pkg:deb/ubuntu/bind9?arch=source&distro=jammyOther threats | Affected
| Fixed in
|
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 should be applied. Fixed versions include 1:9.9.5.dfsg-3ubuntu0.19+esm15, 1:9.10.3.dfsg.P4-8ubuntu1.19+esm11, 1:9.11.3+dfsg-1ubuntu1.19+esm6, 1:9.18.30-0ubuntu0.20.04.2+esm3, 1:9.18.39-0ubuntu0.22.04.7, 1:9.18.39-0ubuntu0.24.04.8, 1:9.20.24-1ubuntu3.1, and 1:9.20.24-1ubuntu0.4. Users should upgrade to these versions or later to remediate the vulnerability. No additional mitigation steps are indicated by the vendor advisory.
Description
Bind9 contains a vulnerability where a validly signed NSEC3 record from an unrelated sibling zone may be accepted as an insecurity proof. This flaw can downgrade a secure delegation and allow a forged unsigned DNS answer to be accepted. The issue affects multiple Bind9 versions ranging from 9.11.0 through 9.21.25 and their respective service pack versions. A fix is available in several updated versions. The vulnerability has a medium severity rating with a CVSS score of 5.9 and does not have known exploits in the wild.