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 | 2026-07-15 02:18:15 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 ADP
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-770 | CWE-606 CWE-606 Unchecked Input for Loop Condition | CWE-770 Allocation of Resources Without Limits or Throttling
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | ADP | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 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 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | 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
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD Known Affected Configurations (CPE 2.3)
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 |
| ADP | Red Hat | Red Hat Enterprise Linux 10 | unaffected 32:9.18.33-10.el10_1.3 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 10.0 Extended Update Support | unaffected 32:9.18.33-4.el10_0.3 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 6 Extended Lifecycle Support - EXTENSION | unaffected 32:9.8.2-0.68.rc1.el6_10.18 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 7 Extended Lifecycle Support | unaffected 32:9.11.4-26.P2.el7_9.20 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8 | unaffected 32:9.16.23-0.22.el8_10.5 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8 | unaffected 32:9.11.36-16.el8_10.7 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support | unaffected 32:9.11.26-4.el8_4.9 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.4 Extended Update Support Long-Life Add-On | unaffected 32:9.11.26-4.el8_4.9 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | unaffected 32:9.11.36-3.el8_6.12 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.6 Advanced Mission Critical Update Support | unaffected 32:9.16.23-0.7.el8_6.10 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.6 Extended Update Support Long-Life Add-On | unaffected 32:9.16.23-0.7.el8_6.10 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.6 Telecommunications Update Service | unaffected 32:9.11.36-3.el8_6.12 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.6 Update Services For SAP Solutions | unaffected 32:9.11.36-3.el8_6.12 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.8 Telecommunications Update Service | unaffected 32:9.11.36-8.el8_8.9 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.8 Telecommunications Update Service | unaffected 32:9.16.23-0.14.el8_8.8 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.8 Update Services For SAP Solutions | unaffected 32:9.11.36-8.el8_8.9 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 8.8 Update Services For SAP Solutions | unaffected 32:9.16.23-0.14.el8_8.8 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9 | unaffected 32:9.18.29-5.el9_7.4 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9 | unaffected 32:9.16.23-34.el9_7.2 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9.2 Update Services For SAP Solutions | unaffected 32:9.16.23-11.el9_2.10 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9.4 Update Services For SAP Solutions | unaffected 32:9.16.23-18.el9_4.11 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9.6 Extended Update Support | unaffected 32:9.16.23-31.el9_6.3 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9.6 Extended Update Support | unaffected 32:9.18.29-4.el9_6.3 * rpm | Not specified |
| ADP | Red Hat | Red Hat OpenShift Container Platform 4.12 | unaffected 412.86.202606251120-0 * rpm | Not specified |
| ADP | Red Hat | Red Hat OpenShift Container Platform 4.19 | unaffected 4.19.9.6.202606241344-0 * rpm | Not specified |
| ADP | Red Hat | Red Hat Hardened Images | unaffected 9.18.48-1.hum1 * rpm | Not specified |
| ADP | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
| ADP | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| access.redhat.com/errata/RHSA-2026:8075 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-1519.json | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | security.access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:8312 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| downloads.isc.org/isc/bind9/9.20.21 | [email protected] | downloads.isc.org | Patch |
| access.redhat.com/errata/RHSA-2026:25171 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:16064 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:11372 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| downloads.isc.org/isc/bind9/9.21.20 | [email protected] | downloads.isc.org | Patch |
| lists.debian.org/debian-lts-announce/2026/04/msg00008.html | af854a3a-2127-422b-91ae-364da2661108 | lists.debian.org | Issue Tracking, Third Party Advisory |
| kb.isc.org/docs/cve-2026-1519 | [email protected] | kb.isc.org | Vendor Advisory |
| access.redhat.com/errata/RHSA-2026:25083 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:24934 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:24851 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:7915 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:8352 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:16060 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:29863 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| downloads.isc.org/isc/bind9/9.18.47 | [email protected] | downloads.isc.org | Patch |
| access.redhat.com/errata/RHSA-2026:25214 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:24500 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:8155 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:15890 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:34048 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-1519 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| bugzilla.redhat.com/show_bug.cgi | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | bugzilla.redhat.com | |
| access.redhat.com/errata/RHSA-2026:11371 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:29110 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| access.redhat.com/errata/RHSA-2026:6935 | 0b0ca135-0b70-47e7-9f44-1890c2a1c46c | access.redhat.com | |
| 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
| Source | Time | Event |
|---|---|---|
| ADP | 2026-03-25T14:01:56.586Z | Reported to Red Hat. |
| ADP | 2026-03-25T13:25:19.802Z | Made public. |
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.
ADP: RHSA-2026:11372: Red Hat Enterprise Linux Server -EXTENSION(v. 6 ELS-EXTENSION), Red Hat Enterprise Linux Server Optional -EXTENSION (v. 6 ELS -EXTENSION)
ADP: RHSA-2026:11371: Red Hat Enterprise Linux Server (v. 7 ELS), Red Hat Enterprise Linux Server Optional (v. 7 ELS)
ADP: RHSA-2026:34048: Red Hat OpenShift Container Platform 4.12
ADP: RHSA-2026:29863: Red Hat OpenShift Container Platform 4.19
ADP: RHSA-2026:24851: Red Hat Enterprise Linux AppStream EUS (v. 10.0)
ADP: RHSA-2026:8312: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)
ADP: RHSA-2026:8352: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux BaseOS (v. 8)
ADP: RHSA-2026:8155: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux CRB (v. 8)
ADP: RHSA-2026:16064: Red Hat Enterprise Linux AppStream AUS (v.8.4), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4), Red Hat Enterprise Linux BaseOS AUS (v.8.4), Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4)
ADP: RHSA-2026:16060: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream E4S (v.8.6), Red Hat Enterprise Linux AppStream TUS (v.8.6), Red Hat Enterprise Linux BaseOS AUS (v.8.6), Red Hat Enterprise Linux BaseOS E4S (v.8.6), Red Hat Enterprise Linux BaseOS TUS (v.8.6)
ADP: RHSA-2026:25171: Red Hat Enterprise Linux AppStream AUS (v.8.6), Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6)
ADP: RHSA-2026:15890: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8), Red Hat Enterprise Linux BaseOS E4S (v.8.8), Red Hat Enterprise Linux BaseOS TUS (v.8.8)
ADP: RHSA-2026:25083: Red Hat Enterprise Linux AppStream E4S (v.8.8), Red Hat Enterprise Linux AppStream TUS (v.8.8)
ADP: RHSA-2026:29110: Red Hat Enterprise Linux AppStream E4S (v.9.2)
ADP: RHSA-2026:25214: Red Hat Enterprise Linux AppStream E4S (v.9.4)
ADP: RHSA-2026:24500: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6)
ADP: RHSA-2026:24934: Red Hat CodeReady Linux Builder EUS (v.9.6), Red Hat Enterprise Linux AppStream EUS (v.9.6)
ADP: RHSA-2026:8075: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)
ADP: RHSA-2026:7915: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)
ADP: RHSA-2026:6935: Red Hat Hardened Images
Workarounds
CNA: This is not recommended, but disabling DNSSEC (`dnssec-validation no;`) prevents exploitation of this issue.
ADP: To mitigate this issue, disable DNSSEC validation on affected BIND resolvers. Alternatively, configure the BIND server as authoritative-only if recursive queries are not required. Disabling DNSSEC validation may reduce the security posture of the DNS resolver. A restart of the BIND service (`named`) is required for these changes to take effect and may temporarily interrupt DNS resolution.
Exploits
CNA: We are not aware of any active exploits.