Excessive NSEC3 iterations cause high CPU load during insecure delegation validation
Summary
| CVE | CVE-2026-1519 |
|---|---|
| State | PUBLISHED |
| Assigner | isc |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-03-25 14:16:33 UTC |
| Updated | 2026-04-13 10:16:11 UTC |
| Description | 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from [email protected]
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS: 0.000680000 probability, percentile 0.208600000 (date 2026-04-15)
Problem Types: CWE-606 | CWE-606 CWE-606 Unchecked Input for Loop Condition
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | DECLARED | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
NoneIntegrity
NoneAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | ISC | BIND 9 | affected 9.11.0 9.16.50 custom | Not specified |
| CNA | ISC | BIND 9 | affected 9.18.0 9.18.46 custom | Not specified |
| CNA | ISC | BIND 9 | affected 9.20.0 9.20.20 custom | Not specified |
| CNA | ISC | BIND 9 | affected 9.21.0 9.21.19 custom | Not specified |
| CNA | ISC | BIND 9 | affected 9.11.3-S1 9.16.50-S1 custom | Not specified |
| CNA | ISC | BIND 9 | affected 9.18.11-S1 9.18.46-S1 custom | Not specified |
| CNA | ISC | BIND 9 | affected 9.20.9-S1 9.20.20-S1 custom | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| downloads.isc.org/isc/bind9/9.20.21 | [email protected] | downloads.isc.org | |
| downloads.isc.org/isc/bind9/9.21.20 | [email protected] | downloads.isc.org | |
| lists.debian.org/debian-lts-announce/2026/04/msg00008.html | af854a3a-2127-422b-91ae-364da2661108 | lists.debian.org | |
| kb.isc.org/docs/cve-2026-1519 | [email protected] | kb.isc.org | |
| downloads.isc.org/isc/bind9/9.18.47 | [email protected] | downloads.isc.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: ISC would like to thank Samy Medjahed/Ap4sh for bringing this vulnerability to our attention. (en)
Additional Advisory Data
Solutions
CNA: Upgrade to the patched release most closely related to your current version of BIND 9: 9.18.47, 9.20.21, 9.21.20, 9.18.47-S1, or 9.20.21-S1.
Workarounds
CNA: This is not recommended, but disabling DNSSEC (`dnssec-validation no;`) prevents exploitation of this issue.
Exploits
CNA: We are not aware of any active exploits.
There are currently no legacy QID mappings associated with this CVE.