CVE-2026-1519
Excessive NSEC3 iterations cause high CPU load during insecure delegation validation
CVSS Score
7.5
EPSS Score
1.5%
EPSS Percentile
72th
If a BIND resolver is performing DNSSEC validation and encounters a maliciously crafted zone, the resolver may consume excessive CPU. Authoritative-only servers are generally unaffected, although there are circumstances where authoritative servers may make recursive queries (see: https://kb.isc.org/docs/why-does-my-authoritative-server-make-recursive-queries). This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.46, 9.20.0 through 9.20.20, 9.21.0 through 9.21.19, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.46-S1, and 9.20.9-S1 through 9.20.20-S1.
| CWE | CWE-606 |
| Vendor | isc |
| Product | bind 9 |
| Published | Mar 25, 2026 |
| Last Updated | Jul 23, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
ISC / BIND 9
9.11.0 ≤ 9.16.50 9.18.0 ≤ 9.18.46 9.20.0 ≤ 9.20.20 9.21.0 ≤ 9.21.19 9.11.3-S1 ≤ 9.16.50-S1 9.18.11-S1 ≤ 9.18.46-S1 9.20.9-S1 ≤ 9.20.20-S1
References
kb.isc.org: https://kb.isc.org/docs/cve-2026-1519 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.18.47 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.20.21 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.21.20 lists.debian.org: https://lists.debian.org/debian-lts-announce/2026/04/msg00008.html access.redhat.com: https://access.redhat.com/security/cve/CVE-2026-1519 bugzilla.redhat.com: https://bugzilla.redhat.com/show_bug.cgi?id=2451305 security.access.redhat.com: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-1519.json access.redhat.com: https://access.redhat.com/errata/RHSA-2026:11372 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:11371 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:34048 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:40021 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:36610 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:29863 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:24851 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:8312 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:8352 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:8155 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:16064 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:16060 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:25171 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:15890 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:25083 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:29110 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:25214 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:24500 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:24934 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:8075 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:7915 access.redhat.com: https://access.redhat.com/errata/RHSA-2026:6935
Credits
ISC would like to thank Samy Medjahed/Ap4sh for bringing this vulnerability to our attention.