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CVE-2026-1519

Excessive NSEC3 iterations cause high CPU load during insecure delegation validation

High7.5EPSS 1.7%
Published
Updated
Reserved
Assigned by
isc

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.

Timeline

  1. ID reserved

    By isc

  2. · 56 days later

    Published

  3. · 6 months later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-1519, by who scored it
Scored byCVSSScoreVector
iscCNA (assigner)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
redhat-SADPADP (enrichment)3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVDNVD · Modified3.1High7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS (exploitation in 30 days)
1.7% · top 23% of all CVEs (7 Nov 2026)
CISA SSVC
Exploitation: none · Automatable: yes · Technical impact: partial
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.5.

Weakness

Affected products

  • ISC · BIND 9

    • affected 9.11.0 – ≤ 9.16.50
    • affected 9.18.0 – ≤ 9.18.46
    • affected 9.20.0 – ≤ 9.20.20
    • affected 9.21.0 – ≤ 9.21.19
    • affected 9.11.3-S1 – ≤ 9.16.50-S1
    • affected 9.18.11-S1 – ≤ 9.18.46-S1
    • affected 9.20.9-S1 – ≤ 9.20.20-S1

What to do

Solution: 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.

Workaround: This is not recommended, but disabling DNSSEC (`dnssec-validation no;`) prevents exploitation of this issue.

Exploitation: We are not aware of any active exploits.

References (34)

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .