CVE intelligence and bounded remediation

CVE-2020-10995 — PowerDNS Recursor from 4.1.0 up to and including 4.3.0 does not sufficiently defend against amplification attacks

High CVSS 7.5

PowerDNS Recursor from 4.1.0 up to and including 4.3.0 does not sufficiently defend against amplification attacks. An issue in the DNS protocol has been found that allow malicious parties to use recursive DNS services to attack third party authoritative name servers. The attack uses a crafted reply by an authoritative name server to amplify the resulting traffic between the recursive and other authoritative name servers. Both types of service can suffer degraded performance as an effect. This is triggered by random subdomains in the NSDNAME in NS records. PowerDNS Recursor 4.1.16, 4.2.2 and 4.3.1 contain a mitigation to limit the impact of this DNS protocol issue.

Severity
High
CVSS
7.5 (3.1)
Published
2020-05-19
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-400

Affected products

  • powerdns / recursor
  • fedoraproject / fedora / 31
  • fedoraproject / fedora / 32
  • debian / debian_linux / 10.0
  • opensuse / backports_sle / 15.0
  • opensuse / leap / 15.1

Matched remediation archetype

Resource exhaustion and denial of service

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Check exposure

  • Identify attacker-influenced work factors including input size, nesting, compression, fan-out, regex cost, allocation, recursion, retries, and connection lifetime.
  • Map per-request and shared CPU, memory, disk, descriptor, thread, queue, and downstream-service limits.
  • Determine whether authentication, tenancy, quotas, and rate controls apply before expensive processing begins.

Remediate safely

  • Bound input size, nesting, expansion, work, concurrency, queue depth, retries, and execution time before resource-intensive processing.
  • Release resources on every success, error, cancellation, and timeout path and use backpressure instead of unbounded buffering.
  • Update affected components and add small deterministic tests that assert resource ceilings rather than exhausting a host.

Authoritative sources

Complete CVE record and remediation plan

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