Vulnerability in BIND 9 resolver state machine during bad-server handling (CVE-2026-5950)
Summary
Vulnerability in BIND 9 resolver state machine during bad-server handling (CVE-2026-5950). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
An unbounded resend loop vulnerability exists in the BIND 9 resolver state machine during bad-server handling, enabling a remote unauthenticated attacker to cause severe resource exhaustion by sending queries that trigger specific retry conditions.
This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through 9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-5950 has been found in BIND 9 resolver state machine during bad-server handling.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "BIND 9 resolver state machine during bad-server handling CVE-2026-5950" on the vendor's site.
CVE-2026-5950 (BIND 9 resolver state machine during bad-server handling) — CWE-606 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-606) exists in BIND 9 resolver state machine during bad-server handling.
Check the vendor advisory for the affected versions of BIND 9 resolver state machine during bad-server handling.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで BIND 9 resolver state machine during bad-server handling を使っているサービスとバージョンを洗い出す。
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2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Alpine Linux ALPINE-CVE-2026-5950 bind Fixed in: 9.18.49-r0
- BellSoft Alpaquita BELL-CVE-2026-5950 bind Fixed in: 9.20.23-r0
- Debian DEBIAN-CVE-2026-5950 bind9
- Ubuntu UBUNTU-CVE-2026-5950 bind9
References
- advisory kb.isc.org
- patch downloads.isc.org
- patch downloads.isc.org
- patch downloads.isc.org
- web nvd.nist.gov
- web github.com