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Vulnerability record · CVE-2020-1350 · published 14 July 2020

CVE-2020-1350: Windows DNS Server improper input validation remote code execution

Microsoft · Windows Server 2008

Windows DNS servers fail to properly handle certain requests, allowing remote code execution. The flaw is network-reachable, needs no authentication or user interaction, and has a critical CVSS score of 10, making it a top-tier risk for any exposed DNS server.

10.0 CVSS 3.1 Critical CISA KEV since 3 Nov 2021 EPSS 97% · top 0.1% CWE-20 · Improper input validation
10.0CVSS 3.1 base score, v2 10.0
97%EPSS exploitation probability, 30 days
YesIn CISA KEV, fix deadline passed
4Affected product versions listed by NVD
5References
17 Jun 2026Last modified by NVD

Description

A remote code execution vulnerability exists in Windows Domain Name System servers when they fail to properly handle requests, aka 'Windows DNS Server Remote Code Execution Vulnerability'.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 17 September 2026. Confidence: high.

critical priorityCVSS 10 with network reachability, no authentication, and KEV listing plus very high EPSS make this an urgent patch-first issue.

What it is

Windows DNS servers fail to properly handle certain requests, allowing remote code execution. The flaw is network-reachable, needs no authentication or user interaction, and has a critical CVSS score of 10, making it a top-tier risk for any exposed DNS server.

Impact

An unauthenticated remote attacker can execute arbitrary code in the context of the DNS service, potentially gaining full control of the server. Because the scope is changed, compromise can extend beyond the DNS service to the host and its domain role.

Attack surface

Reached over the network via DNS requests to a vulnerable Windows DNS server; no authentication or user interaction is required per the CVSS vector (AV:N/PR:N/UI:N). Any server running the affected DNS role and reachable on port 53 is exposed.

Exploitation

Listed in CISA KEV since 2021-11-03 with a required action to apply vendor updates, and EPSS 30-day probability is about 0.91 (99.8th percentile), indicating active exploitation is expected. No ransomware campaign use is documented in this record.

What to do

  • Apply the Microsoft security update referenced in the vendor advisory immediately.
  • Restrict DNS service exposure to trusted networks and block port 53 from untrusted sources where feasible.
  • Enable and review DNS server logging and monitor for anomalous query patterns.
  • Verify all Windows DNS servers in the environment, including legacy 2008/2012/2016/2019 builds, are patched.
  • Track KEV remediation due date (2022-05-03) and confirm closure.

Detection

  • Monitor DNS server logs for malformed or unusually large DNS requests that trigger service errors or crashes.
  • Alert on unexpected process creation or code execution originating from the DNS service process.
  • Watch for DNS service restarts or crashes correlated with inbound query spikes.
  • Use network monitoring to flag anomalous DNS traffic from external sources to internal DNS servers.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Exploitation in the wild

CISA added CVE-2020-1350 to the Known Exploited Vulnerabilities catalog on 3 November 2021 as "Microsoft Windows DNS Server Remote Code Execution Vulnerability". Required action: Apply updates per vendor instructions. Federal deadline 3 May 2022.

Affected products

4 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://packetstormsecurity.com/files/158484/SIGRed-Windows-DNS-Denial-Of-Service.html Third Party AdvisoryVDB Entry
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1350 PatchVendor Advisory
http://packetstormsecurity.com/files/158484/SIGRed-Windows-DNS-Denial-Of-Service.html Third Party AdvisoryVDB Entry
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1350 PatchVendor Advisory
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-1350 US Government Resource

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Source: NIST National Vulnerability Database (record CVE-2020-1350), CISA KEV, FIRST EPSS (scores of 2026-09-24). This page is refreshed as NVD updates the record.